LeetCode Crawler

Description

A Web Crawler Scraping LeetCode Problems info such as Difficulties, Related Questions and Topics.

Data

Main Data CSV

Problems Table Markdown

Problems Table HTML

Requirements

• python3
• requests
• pandas

pip install requests
pip install pandas

Usage

Options

Top Level: main.py

usage: Scrape Extra Info [-h] [-m] [-y] [-t] [-r]

optional arguments:
  -h, --help          show this help message and exit
  -m, --multiprocess  Use Multiprocessing (utilize as many cores as possible)
  -y, --yield_        Use Yield when Sending requests
  -t, --table         Generate Table
  -r, --readme        Generate README

Examples

python main.py -m -t -r     # recommended, otherwise data may not always be up to date

All Problems

id	Title	Difficulty	Paid Only	New Question	Topic Tags	Similar Questions
1	Two Sum	Easy	False	False	Array, Hash Table	3Sum, 4Sum, Two Sum II - Input array is sorted, Two Sum III - Data structure design, Subarray Sum Equals K, Two Sum IV - Input is a BST, Two Sum Less Than K
2	Add Two Numbers	Medium	False	False	Linked List, Math	Multiply Strings, Add Binary, Sum of Two Integers, Add Strings, Add Two Numbers II, Add to Array-Form of Integer
3	Longest Substring Without Repeating Characters	Medium	False	False	Hash Table, Two Pointers, String, Sliding Window	Longest Substring with At Most Two Distinct Characters, Longest Substring with At Most K Distinct Characters, Subarrays with K Different Integers
4	Median of Two Sorted Arrays	Hard	False	False	Array, Binary Search, Divide and Conquer
5	Longest Palindromic Substring	Medium	False	False	String, Dynamic Programming	Shortest Palindrome, Palindrome Permutation, Palindrome Pairs, Longest Palindromic Subsequence, Palindromic Substrings
6	ZigZag Conversion	Medium	False	False	String
7	Reverse Integer	Easy	False	False	Math	String to Integer (atoi), Reverse Bits
8	String to Integer (atoi)	Medium	False	False	Math, String	Reverse Integer, Valid Number
9	Palindrome Number	Easy	False	False	Math	Palindrome Linked List
10	Regular Expression Matching	Hard	False	False	String, Dynamic Programming, Backtracking	Wildcard Matching
11	Container With Most Water	Medium	False	False	Array, Two Pointers	Trapping Rain Water
12	Integer to Roman	Medium	False	False	Math, String	Roman to Integer, Integer to English Words
13	Roman to Integer	Easy	False	False	Math, String	Integer to Roman
14	Longest Common Prefix	Easy	False	False	String
15	3Sum	Medium	False	False	Array, Two Pointers	Two Sum, 3Sum Closest, 4Sum, 3Sum Smaller
16	3Sum Closest	Medium	False	False	Array, Two Pointers	3Sum, 3Sum Smaller
17	Letter Combinations of a Phone Number	Medium	False	False	String, Backtracking	Generate Parentheses, Combination Sum, Binary Watch
18	4Sum	Medium	False	False	Array, Hash Table, Two Pointers	Two Sum, 3Sum, 4Sum II
19	Remove Nth Node From End of List	Medium	False	False	Linked List, Two Pointers	Delete N Nodes After M Nodes of a Linked List
20	Valid Parentheses	Easy	False	False	String, Stack	Generate Parentheses, Longest Valid Parentheses, Remove Invalid Parentheses, Check If Word Is Valid After Substitutions
21	Merge Two Sorted Lists	Easy	False	False	Linked List	Merge k Sorted Lists, Merge Sorted Array, Sort List, Shortest Word Distance II
22	Generate Parentheses	Medium	False	False	String, Backtracking	Letter Combinations of a Phone Number, Valid Parentheses
23	Merge k Sorted Lists	Hard	False	False	Linked List, Divide and Conquer, Heap	Merge Two Sorted Lists, Ugly Number II
24	Swap Nodes in Pairs	Medium	False	False	Linked List	Reverse Nodes in k-Group
25	Reverse Nodes in k-Group	Hard	False	False	Linked List	Swap Nodes in Pairs
26	Remove Duplicates from Sorted Array	Easy	False	False	Array, Two Pointers	Remove Element, Remove Duplicates from Sorted Array II
27	Remove Element	Easy	False	False	Array, Two Pointers	Remove Duplicates from Sorted Array, Remove Linked List Elements, Move Zeroes
28	Implement strStr()	Easy	False	False	Two Pointers, String	Shortest Palindrome, Repeated Substring Pattern
29	Divide Two Integers	Medium	False	False	Math, Binary Search
30	Substring with Concatenation of All Words	Hard	False	False	Hash Table, Two Pointers, String	Minimum Window Substring
31	Next Permutation	Medium	False	False	Array	Permutations, Permutations II, Permutation Sequence, Palindrome Permutation II
32	Longest Valid Parentheses	Hard	False	False	String, Dynamic Programming	Valid Parentheses
33	Search in Rotated Sorted Array	Medium	False	False	Array, Binary Search	Search in Rotated Sorted Array II, Find Minimum in Rotated Sorted Array
34	Find First and Last Position of Element in Sorted Array	Medium	False	False	Array, Binary Search	First Bad Version
35	Search Insert Position	Easy	False	False	Array, Binary Search	First Bad Version
36	Valid Sudoku	Medium	False	False	Hash Table	Sudoku Solver
37	Sudoku Solver	Hard	False	False	Hash Table, Backtracking	Valid Sudoku, Unique Paths III
38	Count and Say	Easy	False	False	String	Encode and Decode Strings, String Compression
39	Combination Sum	Medium	False	False	Array, Backtracking	Letter Combinations of a Phone Number, Combination Sum II, Combinations, Combination Sum III, Factor Combinations, Combination Sum IV
40	Combination Sum II	Medium	False	False	Array, Backtracking	Combination Sum
41	First Missing Positive	Hard	False	False	Array	Missing Number, Find the Duplicate Number, Find All Numbers Disappeared in an Array, Couples Holding Hands
42	Trapping Rain Water	Hard	False	False	Array, Two Pointers, Stack	Container With Most Water, Product of Array Except Self, Trapping Rain Water II, Pour Water
43	Multiply Strings	Medium	False	False	Math, String	Add Two Numbers, Plus One, Add Binary, Add Strings
44	Wildcard Matching	Hard	False	False	String, Dynamic Programming, Backtracking, Greedy	Regular Expression Matching
45	Jump Game II	Hard	False	False	Array, Greedy	Jump Game, Jump Game III
46	Permutations	Medium	False	False	Backtracking	Next Permutation, Permutations II, Permutation Sequence, Combinations
47	Permutations II	Medium	False	False	Backtracking	Next Permutation, Permutations, Palindrome Permutation II, Number of Squareful Arrays
48	Rotate Image	Medium	False	False	Array
49	Group Anagrams	Medium	False	False	Hash Table, String	Valid Anagram, Group Shifted Strings
50	Pow(x, n)	Medium	False	False	Math, Binary Search	Sqrt(x), Super Pow
51	N-Queens	Hard	False	False	Backtracking	N-Queens II, Grid Illumination
52	N-Queens II	Hard	False	False	Backtracking	N-Queens
53	Maximum Subarray	Easy	False	False	Array, Divide and Conquer, Dynamic Programming	Best Time to Buy and Sell Stock, Maximum Product Subarray, Degree of an Array, Longest Turbulent Subarray
54	Spiral Matrix	Medium	False	False	Array	Spiral Matrix II, Spiral Matrix III
55	Jump Game	Medium	False	False	Array, Greedy	Jump Game II, Jump Game III
56	Merge Intervals	Medium	False	False	Array, Sort	Insert Interval, Meeting Rooms, Meeting Rooms II, Teemo Attacking, Add Bold Tag in String, Range Module, Employee Free Time, Partition Labels, Interval List Intersections
57	Insert Interval	Hard	False	False	Array, Sort	Merge Intervals, Range Module
58	Length of Last Word	Easy	False	False	String
59	Spiral Matrix II	Medium	False	False	Array	Spiral Matrix, Spiral Matrix III
60	Permutation Sequence	Hard	False	False	Math, Backtracking	Next Permutation, Permutations
61	Rotate List	Medium	False	False	Linked List, Two Pointers	Rotate Array, Split Linked List in Parts
62	Unique Paths	Medium	False	False	Array, Dynamic Programming	Unique Paths II, Minimum Path Sum, Dungeon Game
63	Unique Paths II	Medium	False	False	Array, Dynamic Programming	Unique Paths, Unique Paths III
64	Minimum Path Sum	Medium	False	False	Array, Dynamic Programming	Unique Paths, Dungeon Game, Cherry Pickup
65	Valid Number	Hard	False	False	Math, String	String to Integer (atoi)
66	Plus One	Easy	False	False	Array	Multiply Strings, Add Binary, Plus One Linked List, Add to Array-Form of Integer
67	Add Binary	Easy	False	False	Math, String	Add Two Numbers, Multiply Strings, Plus One, Add to Array-Form of Integer
68	Text Justification	Hard	False	False	String
69	Sqrt(x)	Easy	False	False	Math, Binary Search	Pow(x, n), Valid Perfect Square
70	Climbing Stairs	Easy	False	False	Dynamic Programming	Min Cost Climbing Stairs, Fibonacci Number, N-th Tribonacci Number
71	Simplify Path	Medium	False	False	String, Stack
72	Edit Distance	Hard	False	False	String, Dynamic Programming	One Edit Distance, Delete Operation for Two Strings, Minimum ASCII Delete Sum for Two Strings, Uncrossed Lines
73	Set Matrix Zeroes	Medium	False	False	Array	Game of Life
74	Search a 2D Matrix	Medium	False	False	Array, Binary Search	Search a 2D Matrix II
75	Sort Colors	Medium	False	False	Array, Two Pointers, Sort	Sort List, Wiggle Sort, Wiggle Sort II
76	Minimum Window Substring	Hard	False	False	Hash Table, Two Pointers, String, Sliding Window	Substring with Concatenation of All Words, Minimum Size Subarray Sum, Sliding Window Maximum, Permutation in String, Smallest Range Covering Elements from K Lists, Minimum Window Subsequence
77	Combinations	Medium	False	False	Backtracking	Combination Sum, Permutations
78	Subsets	Medium	False	False	Array, Backtracking, Bit Manipulation	Subsets II, Generalized Abbreviation, Letter Case Permutation
79	Word Search	Medium	False	False	Array, Backtracking	Word Search II
80	Remove Duplicates from Sorted Array II	Medium	False	False	Array, Two Pointers	Remove Duplicates from Sorted Array
81	Search in Rotated Sorted Array II	Medium	False	False	Array, Binary Search	Search in Rotated Sorted Array
82	Remove Duplicates from Sorted List II	Medium	False	False	Linked List	Remove Duplicates from Sorted List
83	Remove Duplicates from Sorted List	Easy	False	False	Linked List	Remove Duplicates from Sorted List II
84	Largest Rectangle in Histogram	Hard	False	False	Array, Stack	Maximal Rectangle
85	Maximal Rectangle	Hard	False	False	Array, Hash Table, Dynamic Programming, Stack	Largest Rectangle in Histogram, Maximal Square
86	Partition List	Medium	False	False	Linked List, Two Pointers
87	Scramble String	Hard	False	False	String, Dynamic Programming
88	Merge Sorted Array	Easy	False	False	Array, Two Pointers	Merge Two Sorted Lists, Squares of a Sorted Array, Interval List Intersections
89	Gray Code	Medium	False	False	Backtracking	1-bit and 2-bit Characters
90	Subsets II	Medium	False	False	Array, Backtracking	Subsets
91	Decode Ways	Medium	False	False	String, Dynamic Programming	Decode Ways II
92	Reverse Linked List II	Medium	False	False	Linked List	Reverse Linked List
93	Restore IP Addresses	Medium	False	False	String, Backtracking	IP to CIDR
94	Binary Tree Inorder Traversal	Medium	False	False	Hash Table, Stack, Tree	Validate Binary Search Tree, Binary Tree Preorder Traversal, Binary Tree Postorder Traversal, Binary Search Tree Iterator, Kth Smallest Element in a BST, Closest Binary Search Tree Value II, Inorder Successor in BST, Convert Binary Search Tree to Sorted Doubly Linked List, Minimum Distance Between BST Nodes
95	Unique Binary Search Trees II	Medium	False	False	Dynamic Programming, Tree	Unique Binary Search Trees, Different Ways to Add Parentheses
96	Unique Binary Search Trees	Medium	False	False	Dynamic Programming, Tree	Unique Binary Search Trees II
97	Interleaving String	Hard	False	False	String, Dynamic Programming
98	Validate Binary Search Tree	Medium	False	False	Tree, Depth-first Search	Binary Tree Inorder Traversal, Find Mode in Binary Search Tree
99	Recover Binary Search Tree	Hard	False	False	Tree, Depth-first Search
100	Same Tree	Easy	False	False	Tree, Depth-first Search
101	Symmetric Tree	Easy	False	False	Tree, Depth-first Search, Breadth-first Search
102	Binary Tree Level Order Traversal	Medium	False	False	Tree, Breadth-first Search	Binary Tree Zigzag Level Order Traversal, Binary Tree Level Order Traversal II, Minimum Depth of Binary Tree, Binary Tree Vertical Order Traversal, Average of Levels in Binary Tree, N-ary Tree Level Order Traversal, Cousins in Binary Tree
103	Binary Tree Zigzag Level Order Traversal	Medium	False	False	Stack, Tree, Breadth-first Search	Binary Tree Level Order Traversal
104	Maximum Depth of Binary Tree	Easy	False	False	Tree, Depth-first Search	Balanced Binary Tree, Minimum Depth of Binary Tree, Maximum Depth of N-ary Tree, Time Needed to Inform All Employees
105	Construct Binary Tree from Preorder and Inorder Traversal	Medium	False	False	Array, Tree, Depth-first Search	Construct Binary Tree from Inorder and Postorder Traversal
106	Construct Binary Tree from Inorder and Postorder Traversal	Medium	False	False	Array, Tree, Depth-first Search	Construct Binary Tree from Preorder and Inorder Traversal
107	Binary Tree Level Order Traversal II	Easy	False	False	Tree, Breadth-first Search	Binary Tree Level Order Traversal, Average of Levels in Binary Tree
108	Convert Sorted Array to Binary Search Tree	Easy	False	False	Tree, Depth-first Search	Convert Sorted List to Binary Search Tree
109	Convert Sorted List to Binary Search Tree	Medium	False	False	Linked List, Depth-first Search	Convert Sorted Array to Binary Search Tree
110	Balanced Binary Tree	Easy	False	False	Tree, Depth-first Search	Maximum Depth of Binary Tree
111	Minimum Depth of Binary Tree	Easy	False	False	Tree, Depth-first Search, Breadth-first Search	Binary Tree Level Order Traversal, Maximum Depth of Binary Tree
112	Path Sum	Easy	False	False	Tree, Depth-first Search	Path Sum II, Binary Tree Maximum Path Sum, Sum Root to Leaf Numbers, Path Sum III, Path Sum IV
113	Path Sum II	Medium	False	False	Tree, Depth-first Search	Path Sum, Binary Tree Paths, Path Sum III, Path Sum IV
114	Flatten Binary Tree to Linked List	Medium	False	False	Tree, Depth-first Search	Flatten a Multilevel Doubly Linked List
115	Distinct Subsequences	Hard	False	False	String, Dynamic Programming
116	Populating Next Right Pointers in Each Node	Medium	False	False	Tree, Depth-first Search	Populating Next Right Pointers in Each Node II, Binary Tree Right Side View
117	Populating Next Right Pointers in Each Node II	Medium	False	False	Tree, Depth-first Search	Populating Next Right Pointers in Each Node
118	Pascal's Triangle	Easy	False	False	Array	Pascal's Triangle II
119	Pascal's Triangle II	Easy	False	False	Array	Pascal's Triangle
120	Triangle	Medium	False	False	Array, Dynamic Programming
121	Best Time to Buy and Sell Stock	Easy	False	False	Array, Dynamic Programming	Maximum Subarray, Best Time to Buy and Sell Stock II, Best Time to Buy and Sell Stock III, Best Time to Buy and Sell Stock IV, Best Time to Buy and Sell Stock with Cooldown
122	Best Time to Buy and Sell Stock II	Easy	False	False	Array, Greedy	Best Time to Buy and Sell Stock, Best Time to Buy and Sell Stock III, Best Time to Buy and Sell Stock IV, Best Time to Buy and Sell Stock with Cooldown, Best Time to Buy and Sell Stock with Transaction Fee
123	Best Time to Buy and Sell Stock III	Hard	False	False	Array, Dynamic Programming	Best Time to Buy and Sell Stock, Best Time to Buy and Sell Stock II, Best Time to Buy and Sell Stock IV, Maximum Sum of 3 Non-Overlapping Subarrays
124	Binary Tree Maximum Path Sum	Hard	False	False	Tree, Depth-first Search	Path Sum, Sum Root to Leaf Numbers, Path Sum IV, Longest Univalue Path, Time Needed to Inform All Employees
125	Valid Palindrome	Easy	False	False	Two Pointers, String	Palindrome Linked List, Valid Palindrome II
126	Word Ladder II	Hard	False	False	Array, String, Backtracking, Breadth-first Search	Word Ladder
127	Word Ladder	Medium	False	False	Breadth-first Search	Word Ladder II, Minimum Genetic Mutation
128	Longest Consecutive Sequence	Hard	False	False	Array, Union Find	Binary Tree Longest Consecutive Sequence
129	Sum Root to Leaf Numbers	Medium	False	False	Tree, Depth-first Search	Path Sum, Binary Tree Maximum Path Sum, Smallest String Starting From Leaf
130	Surrounded Regions	Medium	False	False	Depth-first Search, Breadth-first Search, Union Find	Number of Islands, Walls and Gates
131	Palindrome Partitioning	Medium	False	False	Backtracking	Palindrome Partitioning II
132	Palindrome Partitioning II	Hard	False	False	Dynamic Programming	Palindrome Partitioning
133	Clone Graph	Medium	False	False	Depth-first Search, Breadth-first Search, Graph	Copy List with Random Pointer, Clone Binary Tree With Random Pointer, Clone N-ary Tree
134	Gas Station	Medium	False	False	Greedy
135	Candy	Hard	False	False	Greedy
136	Single Number	Easy	False	False	Hash Table, Bit Manipulation	Single Number II, Single Number III, Missing Number, Find the Duplicate Number, Find the Difference
137	Single Number II	Medium	False	False	Bit Manipulation	Single Number, Single Number III
138	Copy List with Random Pointer	Medium	False	False	Hash Table, Linked List	Clone Graph, Clone Binary Tree With Random Pointer, Clone N-ary Tree
139	Word Break	Medium	False	False	Dynamic Programming	Word Break II
140	Word Break II	Hard	False	False	Dynamic Programming, Backtracking	Word Break, Concatenated Words
141	Linked List Cycle	Easy	False	False	Linked List, Two Pointers	Linked List Cycle II, Happy Number
142	Linked List Cycle II	Medium	False	False	Linked List, Two Pointers	Linked List Cycle, Find the Duplicate Number
143	Reorder List	Medium	False	False	Linked List
144	Binary Tree Preorder Traversal	Medium	False	False	Stack, Tree	Binary Tree Inorder Traversal, Verify Preorder Sequence in Binary Search Tree, N-ary Tree Preorder Traversal
145	Binary Tree Postorder Traversal	Medium	False	False	Stack, Tree	Binary Tree Inorder Traversal, N-ary Tree Postorder Traversal
146	LRU Cache	Medium	False	False	Design	LFU Cache, Design In-Memory File System, Design Compressed String Iterator
147	Insertion Sort List	Medium	False	False	Linked List, Sort	Sort List, Insert into a Sorted Circular Linked List
148	Sort List	Medium	False	False	Linked List, Sort	Merge Two Sorted Lists, Sort Colors, Insertion Sort List
149	Max Points on a Line	Hard	False	False	Hash Table, Math	Line Reflection
150	Evaluate Reverse Polish Notation	Medium	False	False	Stack	Basic Calculator, Expression Add Operators
151	Reverse Words in a String	Medium	False	False	String	Reverse Words in a String II
152	Maximum Product Subarray	Medium	False	False	Array, Dynamic Programming	Maximum Subarray, House Robber, Product of Array Except Self, Maximum Product of Three Numbers, Subarray Product Less Than K
153	Find Minimum in Rotated Sorted Array	Medium	False	False	Array, Binary Search	Search in Rotated Sorted Array, Find Minimum in Rotated Sorted Array II
154	Find Minimum in Rotated Sorted Array II	Hard	False	False	Array, Binary Search	Find Minimum in Rotated Sorted Array
155	Min Stack	Easy	False	False	Stack, Design	Sliding Window Maximum, Max Stack
156	Binary Tree Upside Down	Medium	True	False	Tree	Reverse Linked List
157	Read N Characters Given Read4	Easy	True	False	String	Read N Characters Given Read4 II - Call multiple times
158	Read N Characters Given Read4 II - Call multiple times	Hard	True	False	String	Read N Characters Given Read4
159	Longest Substring with At Most Two Distinct Characters	Medium	True	False	Hash Table, Two Pointers, String, Sliding Window	Longest Substring Without Repeating Characters, Sliding Window Maximum, Longest Substring with At Most K Distinct Characters, Subarrays with K Different Integers
160	Intersection of Two Linked Lists	Easy	False	False	Linked List	Minimum Index Sum of Two Lists
161	One Edit Distance	Medium	True	False	String	Edit Distance
162	Find Peak Element	Medium	False	False	Array, Binary Search	Peak Index in a Mountain Array
163	Missing Ranges	Medium	True	False	Array	Summary Ranges
164	Maximum Gap	Hard	False	False	Sort
165	Compare Version Numbers	Medium	False	False	String
166	Fraction to Recurring Decimal	Medium	False	False	Hash Table, Math
167	Two Sum II - Input array is sorted	Easy	False	False	Array, Two Pointers, Binary Search	Two Sum, Two Sum IV - Input is a BST, Two Sum Less Than K
168	Excel Sheet Column Title	Easy	False	False	Math	Excel Sheet Column Number
169	Majority Element	Easy	False	False	Array, Divide and Conquer, Bit Manipulation	Majority Element II, Check If a Number Is Majority Element in a Sorted Array
170	Two Sum III - Data structure design	Easy	True	False	Hash Table, Design	Two Sum, Unique Word Abbreviation, Two Sum IV - Input is a BST
171	Excel Sheet Column Number	Easy	False	False	Math	Excel Sheet Column Title
172	Factorial Trailing Zeroes	Easy	False	False	Math	Number of Digit One, Preimage Size of Factorial Zeroes Function
173	Binary Search Tree Iterator	Medium	False	False	Stack, Tree, Design	Binary Tree Inorder Traversal, Flatten 2D Vector, Zigzag Iterator, Peeking Iterator, Inorder Successor in BST
174	Dungeon Game	Hard	False	False	Binary Search, Dynamic Programming	Unique Paths, Minimum Path Sum, Cherry Pickup
175	Combine Two Tables	Easy	False	False		Employee Bonus
176	Second Highest Salary	Easy	False	False
177	Nth Highest Salary	Medium	False	False
178	Rank Scores	Medium	False	False
179	Largest Number	Medium	False	False	Sort
180	Consecutive Numbers	Medium	False	False
181	Employees Earning More Than Their Managers	Easy	False	False
182	Duplicate Emails	Easy	False	False
183	Customers Who Never Order	Easy	False	False
184	Department Highest Salary	Medium	False	False		Highest Grade For Each Student
185	Department Top Three Salaries	Hard	False	False
186	Reverse Words in a String II	Medium	True	False	String	Reverse Words in a String, Rotate Array
187	Repeated DNA Sequences	Medium	False	False	Hash Table, Bit Manipulation
188	Best Time to Buy and Sell Stock IV	Hard	False	False	Dynamic Programming	Best Time to Buy and Sell Stock, Best Time to Buy and Sell Stock II, Best Time to Buy and Sell Stock III
189	Rotate Array	Easy	False	False	Array	Rotate List, Reverse Words in a String II
190	Reverse Bits	Easy	False	False	Bit Manipulation	Reverse Integer, Number of 1 Bits
191	Number of 1 Bits	Easy	False	False	Bit Manipulation	Reverse Bits, Power of Two, Counting Bits, Binary Watch, Hamming Distance, Binary Number with Alternating Bits, Prime Number of Set Bits in Binary Representation
192	Word Frequency	Medium	False	False		Top K Frequent Elements
193	Valid Phone Numbers	Easy	False	False
194	Transpose File	Medium	False	False
195	Tenth Line	Easy	False	False
196	Delete Duplicate Emails	Easy	False	False
197	Rising Temperature	Easy	False	False
198	House Robber	Easy	False	False	Dynamic Programming	Maximum Product Subarray, House Robber II, Paint House, Paint Fence, House Robber III, Non-negative Integers without Consecutive Ones, Coin Path, Delete and Earn
199	Binary Tree Right Side View	Medium	False	False	Tree, Depth-first Search, Breadth-first Search	Populating Next Right Pointers in Each Node, Boundary of Binary Tree
200	Number of Islands	Medium	False	False	Depth-first Search, Breadth-first Search, Union Find	Surrounded Regions, Walls and Gates, Number of Islands II, Number of Connected Components in an Undirected Graph, Number of Distinct Islands, Max Area of Island
201	Bitwise AND of Numbers Range	Medium	False	False	Bit Manipulation
202	Happy Number	Easy	False	False	Hash Table, Math	Linked List Cycle, Add Digits, Ugly Number
203	Remove Linked List Elements	Easy	False	False	Linked List	Remove Element, Delete Node in a Linked List
204	Count Primes	Easy	False	False	Hash Table, Math	Ugly Number, Ugly Number II, Perfect Squares
205	Isomorphic Strings	Easy	False	False	Hash Table	Word Pattern
206	Reverse Linked List	Easy	False	False	Linked List	Reverse Linked List II, Binary Tree Upside Down, Palindrome Linked List
207	Course Schedule	Medium	False	False	Depth-first Search, Breadth-first Search, Graph, Topological Sort	Course Schedule II, Graph Valid Tree, Minimum Height Trees, Course Schedule III
208	Implement Trie (Prefix Tree)	Medium	False	False	Design, Trie	Design Add and Search Words Data Structure, Design Search Autocomplete System, Replace Words, Implement Magic Dictionary
209	Minimum Size Subarray Sum	Medium	False	False	Array, Two Pointers, Binary Search	Minimum Window Substring, Maximum Size Subarray Sum Equals k, Maximum Length of Repeated Subarray
210	Course Schedule II	Medium	False	False	Depth-first Search, Breadth-first Search, Graph, Topological Sort	Course Schedule, Alien Dictionary, Minimum Height Trees, Sequence Reconstruction, Course Schedule III
211	Design Add and Search Words Data Structure	Medium	False	False	Backtracking, Design, Trie	Implement Trie (Prefix Tree), Prefix and Suffix Search
212	Word Search II	Hard	False	False	Backtracking, Trie	Word Search, Unique Paths III
213	House Robber II	Medium	False	False	Dynamic Programming	House Robber, Paint House, Paint Fence, House Robber III, Non-negative Integers without Consecutive Ones, Coin Path
214	Shortest Palindrome	Hard	False	False	String	Longest Palindromic Substring, Implement strStr(), Palindrome Pairs
215	Kth Largest Element in an Array	Medium	False	False	Divide and Conquer, Heap	Wiggle Sort II, Top K Frequent Elements, Third Maximum Number, Kth Largest Element in a Stream, K Closest Points to Origin
216	Combination Sum III	Medium	False	False	Array, Backtracking	Combination Sum
217	Contains Duplicate	Easy	False	False	Array, Hash Table	Contains Duplicate II, Contains Duplicate III
218	The Skyline Problem	Hard	False	False	Divide and Conquer, Heap, Binary Indexed Tree, Segment Tree, Line Sweep	Falling Squares
219	Contains Duplicate II	Easy	False	False	Array, Hash Table	Contains Duplicate, Contains Duplicate III
220	Contains Duplicate III	Medium	False	False	Sort, Ordered Map	Contains Duplicate, Contains Duplicate II
221	Maximal Square	Medium	False	False	Dynamic Programming	Maximal Rectangle, Largest Plus Sign
222	Count Complete Tree Nodes	Medium	False	False	Binary Search, Tree	Closest Binary Search Tree Value
223	Rectangle Area	Medium	False	False	Math	Rectangle Overlap
224	Basic Calculator	Hard	False	False	Math, Stack	Evaluate Reverse Polish Notation, Basic Calculator II, Different Ways to Add Parentheses, Expression Add Operators, Basic Calculator III
225	Implement Stack using Queues	Easy	False	False	Stack, Design	Implement Queue using Stacks
226	Invert Binary Tree	Easy	False	False	Tree
227	Basic Calculator II	Medium	False	False	String	Basic Calculator, Expression Add Operators, Basic Calculator III
228	Summary Ranges	Medium	False	False	Array	Missing Ranges, Data Stream as Disjoint Intervals
229	Majority Element II	Medium	False	False	Array	Majority Element, Check If a Number Is Majority Element in a Sorted Array
230	Kth Smallest Element in a BST	Medium	False	False	Binary Search, Tree	Binary Tree Inorder Traversal, Second Minimum Node In a Binary Tree
231	Power of Two	Easy	False	False	Math, Bit Manipulation	Number of 1 Bits, Power of Three, Power of Four
232	Implement Queue using Stacks	Easy	False	False	Stack, Design	Implement Stack using Queues
233	Number of Digit One	Hard	False	False	Math	Factorial Trailing Zeroes, Digit Count in Range
234	Palindrome Linked List	Easy	False	False	Linked List, Two Pointers	Palindrome Number, Valid Palindrome, Reverse Linked List
235	Lowest Common Ancestor of a Binary Search Tree	Easy	False	False	Tree	Lowest Common Ancestor of a Binary Tree, Smallest Common Region
236	Lowest Common Ancestor of a Binary Tree	Medium	False	False	Tree	Lowest Common Ancestor of a Binary Search Tree, Smallest Common Region
237	Delete Node in a Linked List	Easy	False	False	Linked List	Remove Linked List Elements
238	Product of Array Except Self	Medium	False	False	Array	Trapping Rain Water, Maximum Product Subarray, Paint House II
239	Sliding Window Maximum	Hard	False	False	Heap, Sliding Window	Minimum Window Substring, Min Stack, Longest Substring with At Most Two Distinct Characters, Paint House II
240	Search a 2D Matrix II	Medium	False	False	Binary Search, Divide and Conquer	Search a 2D Matrix
241	Different Ways to Add Parentheses	Medium	False	False	Divide and Conquer	Unique Binary Search Trees II, Basic Calculator, Expression Add Operators
242	Valid Anagram	Easy	False	False	Hash Table, Sort	Group Anagrams, Palindrome Permutation, Find All Anagrams in a String
243	Shortest Word Distance	Easy	True	False	Array	Shortest Word Distance II, Shortest Word Distance III
244	Shortest Word Distance II	Medium	True	False	Hash Table, Design	Merge Two Sorted Lists, Shortest Word Distance, Shortest Word Distance III
245	Shortest Word Distance III	Medium	True	False	Array	Shortest Word Distance, Shortest Word Distance II
246	Strobogrammatic Number	Easy	True	False	Hash Table, Math	Strobogrammatic Number II, Strobogrammatic Number III, Confusing Number
247	Strobogrammatic Number II	Medium	True	False	Math, Recursion	Strobogrammatic Number, Strobogrammatic Number III
248	Strobogrammatic Number III	Hard	True	False	Math, Recursion	Strobogrammatic Number, Strobogrammatic Number II
249	Group Shifted Strings	Medium	True	False	Hash Table, String	Group Anagrams
250	Count Univalue Subtrees	Medium	True	False	Tree	Subtree of Another Tree, Longest Univalue Path
251	Flatten 2D Vector	Medium	True	False	Design	Binary Search Tree Iterator, Zigzag Iterator, Peeking Iterator, Flatten Nested List Iterator
252	Meeting Rooms	Easy	True	False	Sort	Merge Intervals, Meeting Rooms II
253	Meeting Rooms II	Medium	True	False	Heap, Greedy, Sort	Merge Intervals, Meeting Rooms, Minimum Number of Arrows to Burst Balloons, Car Pooling
254	Factor Combinations	Medium	True	False	Backtracking	Combination Sum
255	Verify Preorder Sequence in Binary Search Tree	Medium	True	False	Stack, Tree	Binary Tree Preorder Traversal
256	Paint House	Easy	True	False	Dynamic Programming	House Robber, House Robber II, Paint House II, Paint Fence
257	Binary Tree Paths	Easy	False	False	Tree, Depth-first Search	Path Sum II, Smallest String Starting From Leaf
258	Add Digits	Easy	False	False	Math	Happy Number, Sum of Digits in the Minimum Number
259	3Sum Smaller	Medium	True	False	Array, Two Pointers	3Sum, 3Sum Closest, Valid Triangle Number, Two Sum Less Than K
260	Single Number III	Medium	False	False	Bit Manipulation	Single Number, Single Number II
261	Graph Valid Tree	Medium	True	False	Depth-first Search, Breadth-first Search, Union Find, Graph	Course Schedule, Number of Connected Components in an Undirected Graph
262	Trips and Users	Hard	False	False
263	Ugly Number	Easy	False	False	Math	Happy Number, Count Primes, Ugly Number II
264	Ugly Number II	Medium	False	False	Math, Dynamic Programming, Heap	Merge k Sorted Lists, Count Primes, Ugly Number, Perfect Squares, Super Ugly Number, Ugly Number III
265	Paint House II	Hard	True	False	Dynamic Programming	Product of Array Except Self, Sliding Window Maximum, Paint House, Paint Fence
266	Palindrome Permutation	Easy	True	False	Hash Table	Longest Palindromic Substring, Valid Anagram, Palindrome Permutation II, Longest Palindrome
267	Palindrome Permutation II	Medium	True	False	Backtracking	Next Permutation, Permutations II, Palindrome Permutation
268	Missing Number	Easy	False	False	Array, Math, Bit Manipulation	First Missing Positive, Single Number, Find the Duplicate Number, Couples Holding Hands
269	Alien Dictionary	Hard	True	False	Graph, Topological Sort	Course Schedule II
270	Closest Binary Search Tree Value	Easy	True	False	Binary Search, Tree	Count Complete Tree Nodes, Closest Binary Search Tree Value II, Search in a Binary Search Tree
271	Encode and Decode Strings	Medium	True	False	String	Count and Say, Serialize and Deserialize Binary Tree, String Compression, Count Binary Substrings
272	Closest Binary Search Tree Value II	Hard	True	False	Stack, Tree	Binary Tree Inorder Traversal, Closest Binary Search Tree Value
273	Integer to English Words	Hard	False	False	Math, String	Integer to Roman
274	H-Index	Medium	False	False	Hash Table, Sort	H-Index II
275	H-Index II	Medium	False	False	Binary Search	H-Index
276	Paint Fence	Easy	True	False	Dynamic Programming	House Robber, House Robber II, Paint House, Paint House II
277	Find the Celebrity	Medium	True	False	Array	Find the Town Judge
278	First Bad Version	Easy	False	False	Binary Search	Find First and Last Position of Element in Sorted Array, Search Insert Position, Guess Number Higher or Lower
279	Perfect Squares	Medium	False	False	Math, Dynamic Programming, Breadth-first Search	Count Primes, Ugly Number II
280	Wiggle Sort	Medium	True	False	Array, Sort	Sort Colors, Wiggle Sort II
281	Zigzag Iterator	Medium	True	False	Design	Binary Search Tree Iterator, Flatten 2D Vector, Peeking Iterator, Flatten Nested List Iterator
282	Expression Add Operators	Hard	False	False	Divide and Conquer	Evaluate Reverse Polish Notation, Basic Calculator, Basic Calculator II, Different Ways to Add Parentheses, Target Sum
283	Move Zeroes	Easy	False	False	Array, Two Pointers	Remove Element
284	Peeking Iterator	Medium	False	False	Design	Binary Search Tree Iterator, Flatten 2D Vector, Zigzag Iterator
285	Inorder Successor in BST	Medium	True	False	Tree	Binary Tree Inorder Traversal, Binary Search Tree Iterator, Inorder Successor in BST II
286	Walls and Gates	Medium	True	False	Breadth-first Search	Surrounded Regions, Number of Islands, Shortest Distance from All Buildings, Robot Room Cleaner, Rotting Oranges
287	Find the Duplicate Number	Medium	False	False	Array, Two Pointers, Binary Search	First Missing Positive, Single Number, Linked List Cycle II, Missing Number, Set Mismatch
288	Unique Word Abbreviation	Medium	True	False	Hash Table, Design	Two Sum III - Data structure design, Generalized Abbreviation
289	Game of Life	Medium	False	False	Array	Set Matrix Zeroes
290	Word Pattern	Easy	False	False	Hash Table	Isomorphic Strings, Word Pattern II
291	Word Pattern II	Hard	True	False	Backtracking	Word Pattern
292	Nim Game	Easy	False	False	Brainteaser, Minimax	Flip Game II
293	Flip Game	Easy	True	False	String	Flip Game II
294	Flip Game II	Medium	True	False	Backtracking, Minimax	Nim Game, Flip Game, Guess Number Higher or Lower II, Can I Win
295	Find Median from Data Stream	Hard	False	False	Heap, Design	Sliding Window Median
296	Best Meeting Point	Hard	True	False	Math, Sort	Shortest Distance from All Buildings, Minimum Moves to Equal Array Elements II
297	Serialize and Deserialize Binary Tree	Hard	False	False	Tree, Design	Encode and Decode Strings, Serialize and Deserialize BST, Find Duplicate Subtrees, Serialize and Deserialize N-ary Tree
298	Binary Tree Longest Consecutive Sequence	Medium	True	False	Tree	Longest Consecutive Sequence, Binary Tree Longest Consecutive Sequence II
299	Bulls and Cows	Easy	False	False	Hash Table
300	Longest Increasing Subsequence	Medium	False	False	Binary Search, Dynamic Programming	Increasing Triplet Subsequence, Russian Doll Envelopes, Maximum Length of Pair Chain, Number of Longest Increasing Subsequence, Minimum ASCII Delete Sum for Two Strings
301	Remove Invalid Parentheses	Hard	False	False	Depth-first Search, Breadth-first Search	Valid Parentheses
302	Smallest Rectangle Enclosing Black Pixels	Hard	True	False	Binary Search
303	Range Sum Query - Immutable	Easy	False	False	Dynamic Programming	Range Sum Query 2D - Immutable, Range Sum Query - Mutable, Maximum Size Subarray Sum Equals k
304	Range Sum Query 2D - Immutable	Medium	False	False	Dynamic Programming	Range Sum Query - Immutable, Range Sum Query 2D - Mutable
305	Number of Islands II	Hard	True	False	Union Find	Number of Islands
306	Additive Number	Medium	False	False	Backtracking	Split Array into Fibonacci Sequence
307	Range Sum Query - Mutable	Medium	False	False	Binary Indexed Tree, Segment Tree	Range Sum Query - Immutable, Range Sum Query 2D - Mutable
308	Range Sum Query 2D - Mutable	Hard	True	False	Binary Indexed Tree, Segment Tree	Range Sum Query 2D - Immutable, Range Sum Query - Mutable
309	Best Time to Buy and Sell Stock with Cooldown	Medium	False	False	Dynamic Programming	Best Time to Buy and Sell Stock, Best Time to Buy and Sell Stock II
310	Minimum Height Trees	Medium	False	False	Breadth-first Search, Graph	Course Schedule, Course Schedule II
311	Sparse Matrix Multiplication	Medium	True	False	Hash Table
312	Burst Balloons	Hard	False	False	Divide and Conquer, Dynamic Programming	Minimum Cost to Merge Stones
313	Super Ugly Number	Medium	False	False	Math, Heap	Ugly Number II
314	Binary Tree Vertical Order Traversal	Medium	True	False	Depth-first Search, Breadth-first Search	Binary Tree Level Order Traversal
315	Count of Smaller Numbers After Self	Hard	False	False	Binary Search, Divide and Conquer, Sort, Binary Indexed Tree, Segment Tree	Count of Range Sum, Queue Reconstruction by Height, Reverse Pairs, How Many Numbers Are Smaller Than the Current Number
316	Remove Duplicate Letters	Hard	False	False	Stack, Greedy
317	Shortest Distance from All Buildings	Hard	True	False	Breadth-first Search	Walls and Gates, Best Meeting Point, As Far from Land as Possible
318	Maximum Product of Word Lengths	Medium	False	False	Bit Manipulation
319	Bulb Switcher	Medium	False	False	Math, Brainteaser	Bulb Switcher II, Minimum Number of K Consecutive Bit Flips, Bulb Switcher III
320	Generalized Abbreviation	Medium	True	False	Backtracking, Bit Manipulation	Subsets, Unique Word Abbreviation, Minimum Unique Word Abbreviation
321	Create Maximum Number	Hard	False	False	Dynamic Programming, Greedy	Remove K Digits, Maximum Swap
322	Coin Change	Medium	False	False	Dynamic Programming	Minimum Cost For Tickets
323	Number of Connected Components in an Undirected Graph	Medium	True	False	Depth-first Search, Breadth-first Search, Union Find, Graph	Number of Islands, Graph Valid Tree, Friend Circles
324	Wiggle Sort II	Medium	False	False	Sort	Sort Colors, Kth Largest Element in an Array, Wiggle Sort
325	Maximum Size Subarray Sum Equals k	Medium	True	False	Hash Table	Minimum Size Subarray Sum, Range Sum Query - Immutable, Contiguous Array, Subarray Product Less Than K
326	Power of Three	Easy	False	False	Math	Power of Two, Power of Four
327	Count of Range Sum	Hard	False	False	Binary Search, Divide and Conquer, Sort, Binary Indexed Tree, Segment Tree	Count of Smaller Numbers After Self, Reverse Pairs
328	Odd Even Linked List	Medium	False	False	Linked List	Split Linked List in Parts
329	Longest Increasing Path in a Matrix	Hard	False	False	Depth-first Search, Topological Sort, Memoization
330	Patching Array	Hard	False	False	Greedy
331	Verify Preorder Serialization of a Binary Tree	Medium	False	False	Stack
332	Reconstruct Itinerary	Medium	False	False	Depth-first Search, Graph
333	Largest BST Subtree	Medium	True	False	Tree
334	Increasing Triplet Subsequence	Medium	False	False		Longest Increasing Subsequence
335	Self Crossing	Hard	False	False	Math
336	Palindrome Pairs	Hard	False	False	Hash Table, String, Trie	Longest Palindromic Substring, Shortest Palindrome
337	House Robber III	Medium	False	False	Tree, Depth-first Search	House Robber, House Robber II
338	Counting Bits	Medium	False	False	Dynamic Programming, Bit Manipulation	Number of 1 Bits
339	Nested List Weight Sum	Easy	True	False	Depth-first Search	Nested List Weight Sum II, Array Nesting, Employee Importance
340	Longest Substring with At Most K Distinct Characters	Hard	True	False	Hash Table, String, Sliding Window	Longest Substring Without Repeating Characters, Longest Substring with At Most Two Distinct Characters, Longest Repeating Character Replacement, Subarrays with K Different Integers, Max Consecutive Ones III
341	Flatten Nested List Iterator	Medium	False	False	Stack, Design	Flatten 2D Vector, Zigzag Iterator, Mini Parser, Array Nesting
342	Power of Four	Easy	False	False	Bit Manipulation	Power of Two, Power of Three
343	Integer Break	Medium	False	False	Math, Dynamic Programming
344	Reverse String	Easy	False	False	Two Pointers, String	Reverse Vowels of a String, Reverse String II
345	Reverse Vowels of a String	Easy	False	False	Two Pointers, String	Reverse String, Remove Vowels from a String
346	Moving Average from Data Stream	Easy	True	False	Design, Queue
347	Top K Frequent Elements	Medium	False	False	Hash Table, Heap	Word Frequency, Kth Largest Element in an Array, Sort Characters By Frequency, Split Array into Consecutive Subsequences, Top K Frequent Words, K Closest Points to Origin
348	Design Tic-Tac-Toe	Medium	True	False	Design	Valid Tic-Tac-Toe State
349	Intersection of Two Arrays	Easy	False	False	Hash Table, Two Pointers, Binary Search, Sort	Intersection of Two Arrays II, Intersection of Three Sorted Arrays
350	Intersection of Two Arrays II	Easy	False	False	Hash Table, Two Pointers, Binary Search, Sort	Intersection of Two Arrays, Find Common Characters
351	Android Unlock Patterns	Medium	True	False	Dynamic Programming, Backtracking
352	Data Stream as Disjoint Intervals	Hard	False	False	Binary Search, Ordered Map	Summary Ranges, Find Right Interval, Range Module
353	Design Snake Game	Medium	True	False	Design, Queue
354	Russian Doll Envelopes	Hard	False	False	Binary Search, Dynamic Programming	Longest Increasing Subsequence
355	Design Twitter	Medium	False	False	Hash Table, Heap, Design	Design a File Sharing System
356	Line Reflection	Medium	True	False	Hash Table, Math	Max Points on a Line, Number of Boomerangs
357	Count Numbers with Unique Digits	Medium	False	False	Math, Dynamic Programming, Backtracking
358	Rearrange String k Distance Apart	Hard	True	False	Hash Table, Heap, Greedy	Task Scheduler, Reorganize String
359	Logger Rate Limiter	Easy	True	False	Hash Table, Design	Design Hit Counter
360	Sort Transformed Array	Medium	True	False	Math, Two Pointers, Sort	Squares of a Sorted Array
361	Bomb Enemy	Medium	True	False	Dynamic Programming
362	Design Hit Counter	Medium	True	False	Design	Logger Rate Limiter
363	Max Sum of Rectangle No Larger Than K	Hard	False	False	Binary Search, Dynamic Programming, Queue
364	Nested List Weight Sum II	Medium	True	False	Depth-first Search	Nested List Weight Sum, Array Nesting
365	Water and Jug Problem	Medium	False	False	Math
366	Find Leaves of Binary Tree	Medium	True	False	Tree, Depth-first Search
367	Valid Perfect Square	Easy	False	False	Math, Binary Search	Sqrt(x), Sum of Square Numbers
368	Largest Divisible Subset	Medium	False	False	Math, Dynamic Programming
369	Plus One Linked List	Medium	True	False	Linked List	Plus One
370	Range Addition	Medium	True	False	Array	Range Addition II
371	Sum of Two Integers	Medium	False	False	Bit Manipulation	Add Two Numbers
372	Super Pow	Medium	False	False	Math	Pow(x, n)
373	Find K Pairs with Smallest Sums	Medium	False	False	Heap	Kth Smallest Element in a Sorted Matrix, Find K-th Smallest Pair Distance
374	Guess Number Higher or Lower	Easy	False	False	Binary Search	First Bad Version, Guess Number Higher or Lower II, Find K Closest Elements
375	Guess Number Higher or Lower II	Medium	False	False	Dynamic Programming, Minimax	Flip Game II, Guess Number Higher or Lower, Can I Win, Find K Closest Elements
376	Wiggle Subsequence	Medium	False	False	Dynamic Programming, Greedy
377	Combination Sum IV	Medium	False	False	Dynamic Programming	Combination Sum
378	Kth Smallest Element in a Sorted Matrix	Medium	False	False	Binary Search, Heap	Find K Pairs with Smallest Sums, Kth Smallest Number in Multiplication Table, Find K-th Smallest Pair Distance, K-th Smallest Prime Fraction
379	Design Phone Directory	Medium	True	False	Linked List, Design
380	Insert Delete GetRandom O(1)	Medium	False	False	Array, Hash Table, Design	Insert Delete GetRandom O(1) - Duplicates allowed
381	Insert Delete GetRandom O(1) - Duplicates allowed	Hard	False	False	Array, Hash Table, Design	Insert Delete GetRandom O(1)
382	Linked List Random Node	Medium	False	False	Reservoir Sampling	Random Pick Index
383	Ransom Note	Easy	False	False	String	Stickers to Spell Word
384	Shuffle an Array	Medium	False	False
385	Mini Parser	Medium	False	False	String, Stack	Flatten Nested List Iterator, Ternary Expression Parser, Remove Comments
386	Lexicographical Numbers	Medium	False	False
387	First Unique Character in a String	Easy	False	False	Hash Table, String	Sort Characters By Frequency
388	Longest Absolute File Path	Medium	False	False
389	Find the Difference	Easy	False	False	Hash Table, Bit Manipulation	Single Number
390	Elimination Game	Medium	False	False
391	Perfect Rectangle	Hard	False	False	Line Sweep
392	Is Subsequence	Easy	False	False	Binary Search, Dynamic Programming, Greedy	Number of Matching Subsequences, Shortest Way to Form String
393	UTF-8 Validation	Medium	False	False	Bit Manipulation
394	Decode String	Medium	False	False	Stack, Depth-first Search	Encode String with Shortest Length, Number of Atoms, Brace Expansion
395	Longest Substring with At Least K Repeating Characters	Medium	False	False
396	Rotate Function	Medium	False	False	Math
397	Integer Replacement	Medium	False	False	Math, Bit Manipulation
398	Random Pick Index	Medium	False	False	Reservoir Sampling	Linked List Random Node, Random Pick with Blacklist, Random Pick with Weight
399	Evaluate Division	Medium	False	False	Union Find, Graph
400	Nth Digit	Medium	False	False	Math
401	Binary Watch	Easy	False	False	Backtracking, Bit Manipulation	Letter Combinations of a Phone Number, Number of 1 Bits
402	Remove K Digits	Medium	False	False	Stack, Greedy	Create Maximum Number, Monotone Increasing Digits
403	Frog Jump	Hard	False	False	Dynamic Programming
404	Sum of Left Leaves	Easy	False	False	Tree
405	Convert a Number to Hexadecimal	Easy	False	False	Bit Manipulation
406	Queue Reconstruction by Height	Medium	False	False	Greedy	Count of Smaller Numbers After Self
407	Trapping Rain Water II	Hard	False	False	Heap, Breadth-first Search	Trapping Rain Water
408	Valid Word Abbreviation	Easy	True	False	String	Minimum Unique Word Abbreviation, Word Abbreviation
409	Longest Palindrome	Easy	False	False	Hash Table	Palindrome Permutation
410	Split Array Largest Sum	Hard	False	False	Binary Search, Dynamic Programming
411	Minimum Unique Word Abbreviation	Hard	True	False	Backtracking, Bit Manipulation	Generalized Abbreviation, Valid Word Abbreviation, Word Abbreviation
412	Fizz Buzz	Easy	False	False		Fizz Buzz Multithreaded
413	Arithmetic Slices	Medium	False	False	Math, Dynamic Programming	Arithmetic Slices II - Subsequence
414	Third Maximum Number	Easy	False	False	Array	Kth Largest Element in an Array
415	Add Strings	Easy	False	False	String	Add Two Numbers, Multiply Strings, Add to Array-Form of Integer
416	Partition Equal Subset Sum	Medium	False	False	Dynamic Programming	Partition to K Equal Sum Subsets
417	Pacific Atlantic Water Flow	Medium	False	False	Depth-first Search, Breadth-first Search
418	Sentence Screen Fitting	Medium	True	False	Dynamic Programming
419	Battleships in a Board	Medium	False	False
420	Strong Password Checker	Hard	False	False
421	Maximum XOR of Two Numbers in an Array	Medium	False	False	Bit Manipulation, Trie
422	Valid Word Square	Easy	True	False		Word Squares, Toeplitz Matrix
423	Reconstruct Original Digits from English	Medium	False	False	Math
424	Longest Repeating Character Replacement	Medium	False	False	Two Pointers, Sliding Window	Longest Substring with At Most K Distinct Characters, Max Consecutive Ones III
425	Word Squares	Hard	True	False	Backtracking, Trie	Valid Word Square
432	All O`one Data Structure	Hard	False	False	Design
433	Minimum Genetic Mutation	Medium	False	False		Word Ladder
434	Number of Segments in a String	Easy	False	False	String
435	Non-overlapping Intervals	Medium	False	False	Greedy	Minimum Number of Arrows to Burst Balloons
436	Find Right Interval	Medium	False	False	Binary Search	Data Stream as Disjoint Intervals
437	Path Sum III	Medium	False	False	Tree	Path Sum, Path Sum II, Path Sum IV, Longest Univalue Path
438	Find All Anagrams in a String	Medium	False	False	Hash Table	Valid Anagram, Permutation in String
439	Ternary Expression Parser	Medium	True	False	Stack, Depth-first Search	Mini Parser, Remove Comments, Parse Lisp Expression
440	K-th Smallest in Lexicographical Order	Hard	False	False
441	Arranging Coins	Easy	False	False	Math, Binary Search
442	Find All Duplicates in an Array	Medium	False	False	Array	Find All Numbers Disappeared in an Array
443	String Compression	Easy	False	False	String	Count and Say, Encode and Decode Strings, Design Compressed String Iterator, Decompress Run-Length Encoded List
444	Sequence Reconstruction	Medium	True	False	Graph, Topological Sort	Course Schedule II
445	Add Two Numbers II	Medium	False	False	Linked List	Add Two Numbers
446	Arithmetic Slices II - Subsequence	Hard	False	False	Dynamic Programming	Arithmetic Slices
447	Number of Boomerangs	Easy	False	False	Hash Table	Line Reflection
448	Find All Numbers Disappeared in an Array	Easy	False	False	Array	First Missing Positive, Find All Duplicates in an Array
449	Serialize and Deserialize BST	Medium	False	False	Tree	Serialize and Deserialize Binary Tree, Find Duplicate Subtrees, Serialize and Deserialize N-ary Tree
450	Delete Node in a BST	Medium	False	False	Tree	Split BST
451	Sort Characters By Frequency	Medium	False	False	Hash Table, Heap	Top K Frequent Elements, First Unique Character in a String
452	Minimum Number of Arrows to Burst Balloons	Medium	False	False	Greedy	Meeting Rooms II, Non-overlapping Intervals
453	Minimum Moves to Equal Array Elements	Easy	False	False	Math	Minimum Moves to Equal Array Elements II
454	4Sum II	Medium	False	False	Hash Table, Binary Search	4Sum
455	Assign Cookies	Easy	False	False	Greedy
456	132 Pattern	Medium	False	False	Stack
457	Circular Array Loop	Medium	False	False	Array, Two Pointers
458	Poor Pigs	Hard	False	False	Math
459	Repeated Substring Pattern	Easy	False	False	String	Implement strStr(), Repeated String Match
460	LFU Cache	Hard	False	False	Design	LRU Cache, Design In-Memory File System
461	Hamming Distance	Easy	False	False	Bit Manipulation	Number of 1 Bits, Total Hamming Distance
462	Minimum Moves to Equal Array Elements II	Medium	False	False	Math	Best Meeting Point, Minimum Moves to Equal Array Elements
463	Island Perimeter	Easy	False	False	Hash Table	Max Area of Island, Flood Fill, Coloring A Border
464	Can I Win	Medium	False	False	Dynamic Programming, Minimax	Flip Game II, Guess Number Higher or Lower II, Predict the Winner
465	Optimal Account Balancing	Hard	True	False
466	Count The Repetitions	Hard	False	False	Dynamic Programming
467	Unique Substrings in Wraparound String	Medium	False	False	Dynamic Programming
468	Validate IP Address	Medium	False	False	String	IP to CIDR
469	Convex Polygon	Medium	True	False	Math
471	Encode String with Shortest Length	Hard	True	False	Dynamic Programming	Decode String, Number of Atoms
472	Concatenated Words	Hard	False	False	Dynamic Programming, Depth-first Search, Trie	Word Break II
473	Matchsticks to Square	Medium	False	False	Depth-first Search
474	Ones and Zeroes	Medium	False	False	Dynamic Programming	Non-negative Integers without Consecutive Ones
475	Heaters	Easy	False	False	Binary Search
476	Number Complement	Easy	False	False	Bit Manipulation
477	Total Hamming Distance	Medium	False	False	Bit Manipulation	Hamming Distance
479	Largest Palindrome Product	Hard	False	False
480	Sliding Window Median	Hard	False	False	Sliding Window	Find Median from Data Stream
481	Magical String	Medium	False	False
482	License Key Formatting	Easy	False	False
483	Smallest Good Base	Hard	False	False	Math, Binary Search
484	Find Permutation	Medium	True	False	Greedy
485	Max Consecutive Ones	Easy	False	False	Array	Max Consecutive Ones II, Max Consecutive Ones III, Consecutive Characters
486	Predict the Winner	Medium	False	False	Dynamic Programming, Minimax	Can I Win
487	Max Consecutive Ones II	Medium	True	False	Two Pointers	Max Consecutive Ones, Max Consecutive Ones III
488	Zuma Game	Hard	False	False	Depth-first Search
490	The Maze	Medium	True	False	Depth-first Search, Breadth-first Search	The Maze III, The Maze II
491	Increasing Subsequences	Medium	False	False	Depth-first Search	Maximum Length of Pair Chain
492	Construct the Rectangle	Easy	False	False
493	Reverse Pairs	Hard	False	False	Binary Search, Divide and Conquer, Sort, Binary Indexed Tree, Segment Tree	Count of Smaller Numbers After Self, Count of Range Sum
494	Target Sum	Medium	False	False	Dynamic Programming, Depth-first Search	Expression Add Operators
495	Teemo Attacking	Medium	False	False	Array	Merge Intervals, Can Place Flowers, Dota2 Senate
496	Next Greater Element I	Easy	False	False	Stack	Next Greater Element II, Next Greater Element III, Daily Temperatures
498	Diagonal Traverse	Medium	False	False
499	The Maze III	Hard	True	False	Depth-first Search, Breadth-first Search	The Maze, The Maze II
500	Keyboard Row	Easy	False	False	Hash Table
501	Find Mode in Binary Search Tree	Easy	False	False	Tree	Validate Binary Search Tree
502	IPO	Hard	False	False	Heap, Greedy
503	Next Greater Element II	Medium	False	False	Stack	Next Greater Element I, Next Greater Element III
504	Base 7	Easy	False	False
505	The Maze II	Medium	True	False	Depth-first Search, Breadth-first Search	The Maze, The Maze III
506	Relative Ranks	Easy	False	False
507	Perfect Number	Easy	False	False	Math	Self Dividing Numbers
508	Most Frequent Subtree Sum	Medium	False	False	Hash Table, Tree	Subtree of Another Tree
510	Inorder Successor in BST II	Medium	True	False	Tree	Inorder Successor in BST
1059	All Paths from Source Lead to Destination	Medium	True	False	Depth-first Search, Graph
513	Find Bottom Left Tree Value	Medium	False	False	Tree, Depth-first Search, Breadth-first Search
514	Freedom Trail	Hard	False	False	Divide and Conquer, Dynamic Programming, Depth-first Search
515	Find Largest Value in Each Tree Row	Medium	False	False	Tree, Depth-first Search, Breadth-first Search
516	Longest Palindromic Subsequence	Medium	False	False	Dynamic Programming	Longest Palindromic Substring, Palindromic Substrings, Count Different Palindromic Subsequences, Longest Common Subsequence
517	Super Washing Machines	Hard	False	False	Math, Dynamic Programming
518	Coin Change 2	Medium	False	False
520	Detect Capital	Easy	False	False	String
521	Longest Uncommon Subsequence I	Easy	False	False	String, Brainteaser	Longest Uncommon Subsequence II
522	Longest Uncommon Subsequence II	Medium	False	False	String	Longest Uncommon Subsequence I
523	Continuous Subarray Sum	Medium	False	False	Math, Dynamic Programming	Subarray Sum Equals K
524	Longest Word in Dictionary through Deleting	Medium	False	False	Two Pointers, Sort	Longest Word in Dictionary
525	Contiguous Array	Medium	False	False	Hash Table	Maximum Size Subarray Sum Equals k
526	Beautiful Arrangement	Medium	False	False	Backtracking	Beautiful Arrangement II
527	Word Abbreviation	Hard	True	False	String, Sort	Valid Word Abbreviation, Minimum Unique Word Abbreviation
529	Minesweeper	Medium	False	False	Depth-first Search, Breadth-first Search
530	Minimum Absolute Difference in BST	Easy	False	False	Tree	K-diff Pairs in an Array
531	Lonely Pixel I	Medium	True	False	Array, Depth-first Search	Lonely Pixel II
532	K-diff Pairs in an Array	Easy	False	False	Array, Two Pointers	Minimum Absolute Difference in BST
533	Lonely Pixel II	Medium	True	False	Array	Lonely Pixel I
535	Encode and Decode TinyURL	Medium	False	False	Hash Table, Math
536	Construct Binary Tree from String	Medium	True	False	String, Tree	Construct String from Binary Tree
537	Complex Number Multiplication	Medium	False	False	Math, String
538	Convert BST to Greater Tree	Easy	False	False	Tree
539	Minimum Time Difference	Medium	False	False	String
540	Single Element in a Sorted Array	Medium	False	False
541	Reverse String II	Easy	False	False	String	Reverse String, Reverse Words in a String III
542	01 Matrix	Medium	False	False	Depth-first Search, Breadth-first Search
543	Diameter of Binary Tree	Easy	False	False	Tree	Diameter of N-Ary Tree
544	Output Contest Matches	Medium	True	False	String, Recursion
545	Boundary of Binary Tree	Medium	True	False	Tree	Binary Tree Right Side View
546	Remove Boxes	Hard	False	False	Dynamic Programming, Depth-first Search	Strange Printer
547	Friend Circles	Medium	False	False	Depth-first Search, Union Find	Number of Connected Components in an Undirected Graph, Robot Return to Origin, Sentence Similarity, Sentence Similarity II, The Earliest Moment When Everyone Become Friends
548	Split Array with Equal Sum	Medium	True	False	Array	Number of Ways to Split a String
549	Binary Tree Longest Consecutive Sequence II	Medium	True	False	Tree	Binary Tree Longest Consecutive Sequence
551	Student Attendance Record I	Easy	False	False	String	Student Attendance Record II
552	Student Attendance Record II	Hard	False	False	Dynamic Programming	Student Attendance Record I
553	Optimal Division	Medium	False	False	Math, String
554	Brick Wall	Medium	False	False	Hash Table
555	Split Concatenated Strings	Medium	True	False	String
556	Next Greater Element III	Medium	False	False	String	Next Greater Element I, Next Greater Element II
557	Reverse Words in a String III	Easy	False	False	String	Reverse String II
560	Subarray Sum Equals K	Medium	False	False	Array, Hash Table	Two Sum, Continuous Subarray Sum, Subarray Product Less Than K, Find Pivot Index, Subarray Sums Divisible by K
561	Array Partition I	Easy	False	False	Array
562	Longest Line of Consecutive One in Matrix	Medium	True	False	Array
563	Binary Tree Tilt	Easy	False	False	Tree	Find All The Lonely Nodes
564	Find the Closest Palindrome	Hard	False	False	String
565	Array Nesting	Medium	False	False	Array	Nested List Weight Sum, Flatten Nested List Iterator, Nested List Weight Sum II
566	Reshape the Matrix	Easy	False	False	Array
567	Permutation in String	Medium	False	False	Two Pointers, Sliding Window	Minimum Window Substring, Find All Anagrams in a String
568	Maximum Vacation Days	Hard	True	False	Dynamic Programming	Cheapest Flights Within K Stops
569	Median Employee Salary	Hard	True	False		Find Median Given Frequency of Numbers
570	Managers with at Least 5 Direct Reports	Medium	True	False
571	Find Median Given Frequency of Numbers	Hard	True	False		Median Employee Salary
572	Subtree of Another Tree	Easy	False	False	Tree	Count Univalue Subtrees, Most Frequent Subtree Sum
573	Squirrel Simulation	Medium	True	False	Math
574	Winning Candidate	Medium	True	False
575	Distribute Candies	Easy	False	False	Hash Table
576	Out of Boundary Paths	Medium	False	False	Dynamic Programming, Depth-first Search	Knight Probability in Chessboard
577	Employee Bonus	Easy	True	False		Combine Two Tables
578	Get Highest Answer Rate Question	Medium	True	False
579	Find Cumulative Salary of an Employee	Hard	True	False
580	Count Student Number in Departments	Medium	True	False
581	Shortest Unsorted Continuous Subarray	Easy	False	False	Array
582	Kill Process	Medium	True	False	Tree, Queue
583	Delete Operation for Two Strings	Medium	False	False	String	Edit Distance, Minimum ASCII Delete Sum for Two Strings, Longest Common Subsequence
584	Find Customer Referee	Easy	True	False
585	Investments in 2016	Medium	True	False
586	Customer Placing the Largest Number of Orders	Easy	True	False
587	Erect the Fence	Hard	False	False	Geometry
588	Design In-Memory File System	Hard	True	False	Design	LRU Cache, LFU Cache, Design Log Storage System
591	Tag Validator	Hard	False	False	String, Stack	Add Bold Tag in String
592	Fraction Addition and Subtraction	Medium	False	False	Math	Solve the Equation
593	Valid Square	Medium	False	False	Math
594	Longest Harmonious Subsequence	Easy	False	False	Hash Table
595	Big Countries	Easy	False	False
596	Classes More Than 5 Students	Easy	False	False
597	Friend Requests I: Overall Acceptance Rate	Easy	True	False
598	Range Addition II	Easy	False	False	Math	Range Addition
599	Minimum Index Sum of Two Lists	Easy	False	False	Hash Table	Intersection of Two Linked Lists
600	Non-negative Integers without Consecutive Ones	Hard	False	False	Dynamic Programming	House Robber, House Robber II, Ones and Zeroes
601	Human Traffic of Stadium	Hard	False	False
602	Friend Requests II: Who Has the Most Friends	Medium	True	False
603	Consecutive Available Seats	Easy	True	False
604	Design Compressed String Iterator	Easy	True	False	Design	LRU Cache, String Compression
605	Can Place Flowers	Easy	False	False	Array	Teemo Attacking, Asteroid Collision
606	Construct String from Binary Tree	Easy	False	False	String, Tree	Construct Binary Tree from String, Find Duplicate Subtrees
607	Sales Person	Easy	True	False
608	Tree Node	Medium	True	False
609	Find Duplicate File in System	Medium	False	False	Hash Table, String
610	Triangle Judgement	Easy	True	False
611	Valid Triangle Number	Medium	False	False	Array	3Sum Smaller
612	Shortest Distance in a Plane	Medium	True	False
613	Shortest Distance in a Line	Easy	True	False
614	Second Degree Follower	Medium	True	False
615	Average Salary: Departments VS Company	Hard	True	False		Countries You Can Safely Invest In
616	Add Bold Tag in String	Medium	True	False	String	Merge Intervals, Tag Validator
617	Merge Two Binary Trees	Easy	False	False	Tree
618	Students Report By Geography	Hard	True	False
619	Biggest Single Number	Easy	True	False
620	Not Boring Movies	Easy	False	False
621	Task Scheduler	Medium	False	False	Array, Greedy, Queue	Rearrange String k Distance Apart, Reorganize String
623	Add One Row to Tree	Medium	False	False	Tree
624	Maximum Distance in Arrays	Easy	True	False	Array, Hash Table
625	Minimum Factorization	Medium	True	False	Math, Recursion
626	Exchange Seats	Medium	False	False
627	Swap Salary	Easy	False	False
628	Maximum Product of Three Numbers	Easy	False	False	Array, Math	Maximum Product Subarray
629	K Inverse Pairs Array	Hard	False	False	Dynamic Programming
630	Course Schedule III	Hard	False	False	Greedy	Course Schedule, Course Schedule II
631	Design Excel Sum Formula	Hard	True	False	Design
632	Smallest Range Covering Elements from K Lists	Hard	False	False	Hash Table, Two Pointers, String	Minimum Window Substring
633	Sum of Square Numbers	Easy	False	False	Math	Valid Perfect Square
634	Find the Derangement of An Array	Medium	True	False	Math
635	Design Log Storage System	Medium	True	False	String, Design	Design In-Memory File System
636	Exclusive Time of Functions	Medium	False	False	Stack
637	Average of Levels in Binary Tree	Easy	False	False	Tree	Binary Tree Level Order Traversal, Binary Tree Level Order Traversal II
638	Shopping Offers	Medium	False	False	Dynamic Programming, Depth-first Search
639	Decode Ways II	Hard	False	False	Dynamic Programming	Decode Ways
640	Solve the Equation	Medium	False	False	Math	Fraction Addition and Subtraction
642	Design Search Autocomplete System	Hard	True	False	Design, Trie	Implement Trie (Prefix Tree)
643	Maximum Average Subarray I	Easy	False	False	Array	Maximum Average Subarray II
644	Maximum Average Subarray II	Hard	True	False	Array, Binary Search	Maximum Average Subarray I
645	Set Mismatch	Easy	False	False	Hash Table, Math	Find the Duplicate Number
646	Maximum Length of Pair Chain	Medium	False	False	Dynamic Programming	Longest Increasing Subsequence, Increasing Subsequences
647	Palindromic Substrings	Medium	False	False	String, Dynamic Programming	Longest Palindromic Substring, Longest Palindromic Subsequence
648	Replace Words	Medium	False	False	Hash Table, Trie	Implement Trie (Prefix Tree)
649	Dota2 Senate	Medium	False	False	Greedy	Teemo Attacking
650	2 Keys Keyboard	Medium	False	False	Dynamic Programming	4 Keys Keyboard, Broken Calculator
651	4 Keys Keyboard	Medium	True	False	Math, Dynamic Programming, Greedy	2 Keys Keyboard
652	Find Duplicate Subtrees	Medium	False	False	Tree	Serialize and Deserialize Binary Tree, Serialize and Deserialize BST, Construct String from Binary Tree
653	Two Sum IV - Input is a BST	Easy	False	False	Tree	Two Sum, Two Sum II - Input array is sorted, Two Sum III - Data structure design, Two Sum BSTs
654	Maximum Binary Tree	Medium	False	False	Tree	Maximum Binary Tree II
655	Print Binary Tree	Medium	False	False	Tree
656	Coin Path	Hard	True	False	Dynamic Programming	House Robber, House Robber II
657	Robot Return to Origin	Easy	False	False	String	Friend Circles
658	Find K Closest Elements	Medium	False	False	Binary Search	Guess Number Higher or Lower, Guess Number Higher or Lower II, Find K-th Smallest Pair Distance
659	Split Array into Consecutive Subsequences	Medium	False	False	Heap, Greedy	Top K Frequent Elements, Divide Array in Sets of K Consecutive Numbers
660	Remove 9	Hard	True	False	Math
661	Image Smoother	Easy	False	False	Array
662	Maximum Width of Binary Tree	Medium	False	False	Tree
663	Equal Tree Partition	Medium	True	False	Tree
664	Strange Printer	Hard	False	False	Dynamic Programming, Depth-first Search	Remove Boxes
665	Non-decreasing Array	Easy	False	False	Array
666	Path Sum IV	Medium	True	False	Tree	Path Sum, Path Sum II, Binary Tree Maximum Path Sum, Path Sum III
667	Beautiful Arrangement II	Medium	False	False	Array	Beautiful Arrangement
668	Kth Smallest Number in Multiplication Table	Hard	False	False	Binary Search	Kth Smallest Element in a Sorted Matrix, Find K-th Smallest Pair Distance, K-th Smallest Prime Fraction
669	Trim a Binary Search Tree	Easy	False	False	Tree
670	Maximum Swap	Medium	False	False	Array, Math	Create Maximum Number
671	Second Minimum Node In a Binary Tree	Easy	False	False	Tree	Kth Smallest Element in a BST
672	Bulb Switcher II	Medium	False	False	Math	Bulb Switcher, Bulb Switcher III
673	Number of Longest Increasing Subsequence	Medium	False	False	Dynamic Programming	Longest Increasing Subsequence, Longest Continuous Increasing Subsequence
674	Longest Continuous Increasing Subsequence	Easy	False	False	Array	Number of Longest Increasing Subsequence, Minimum Window Subsequence
675	Cut Off Trees for Golf Event	Hard	False	False	Breadth-first Search
676	Implement Magic Dictionary	Medium	False	False	Hash Table, Trie	Implement Trie (Prefix Tree), Longest Word in Dictionary
677	Map Sum Pairs	Medium	False	False	Trie
678	Valid Parenthesis String	Medium	False	False	String	Special Binary String
679	24 Game	Hard	False	False	Depth-first Search
680	Valid Palindrome II	Easy	False	False	String	Valid Palindrome
681	Next Closest Time	Medium	True	False	String
682	Baseball Game	Easy	False	False	Stack
683	K Empty Slots	Hard	True	False	Ordered Map
684	Redundant Connection	Medium	False	False	Tree, Union Find, Graph	Redundant Connection II, Accounts Merge
685	Redundant Connection II	Hard	False	False	Tree, Depth-first Search, Union Find, Graph	Redundant Connection
686	Repeated String Match	Medium	False	False	String	Repeated Substring Pattern
687	Longest Univalue Path	Easy	False	False	Tree, Recursion	Binary Tree Maximum Path Sum, Count Univalue Subtrees, Path Sum III
688	Knight Probability in Chessboard	Medium	False	False	Dynamic Programming	Out of Boundary Paths
689	Maximum Sum of 3 Non-Overlapping Subarrays	Hard	False	False	Array, Dynamic Programming	Best Time to Buy and Sell Stock III
690	Employee Importance	Easy	False	False	Hash Table, Depth-first Search, Breadth-first Search	Nested List Weight Sum
691	Stickers to Spell Word	Hard	False	False	Dynamic Programming, Backtracking	Ransom Note
692	Top K Frequent Words	Medium	False	False	Hash Table, Heap, Trie	Top K Frequent Elements, K Closest Points to Origin
693	Binary Number with Alternating Bits	Easy	False	False	Bit Manipulation	Number of 1 Bits
694	Number of Distinct Islands	Medium	True	False	Hash Table, Depth-first Search	Number of Islands, Number of Distinct Islands II
695	Max Area of Island	Medium	False	False	Array, Depth-first Search	Number of Islands, Island Perimeter
696	Count Binary Substrings	Easy	False	False	String	Encode and Decode Strings
697	Degree of an Array	Easy	False	False	Array	Maximum Subarray
698	Partition to K Equal Sum Subsets	Medium	False	False	Dynamic Programming, Recursion	Partition Equal Subset Sum
699	Falling Squares	Hard	False	False	Segment Tree, Ordered Map	The Skyline Problem
711	Number of Distinct Islands II	Hard	True	False	Hash Table, Depth-first Search	Number of Distinct Islands
712	Minimum ASCII Delete Sum for Two Strings	Medium	False	False	Dynamic Programming	Edit Distance, Longest Increasing Subsequence, Delete Operation for Two Strings
713	Subarray Product Less Than K	Medium	False	False	Array, Two Pointers	Maximum Product Subarray, Maximum Size Subarray Sum Equals k, Subarray Sum Equals K, Two Sum Less Than K
714	Best Time to Buy and Sell Stock with Transaction Fee	Medium	False	False	Array, Dynamic Programming, Greedy	Best Time to Buy and Sell Stock II
715	Range Module	Hard	False	False	Segment Tree, Ordered Map	Merge Intervals, Insert Interval, Data Stream as Disjoint Intervals
716	Max Stack	Easy	True	False	Design	Min Stack
717	1-bit and 2-bit Characters	Easy	False	False	Array	Gray Code
718	Maximum Length of Repeated Subarray	Medium	False	False	Array, Hash Table, Binary Search, Dynamic Programming	Minimum Size Subarray Sum
719	Find K-th Smallest Pair Distance	Hard	False	False	Array, Binary Search, Heap	Find K Pairs with Smallest Sums, Kth Smallest Element in a Sorted Matrix, Find K Closest Elements, Kth Smallest Number in Multiplication Table, K-th Smallest Prime Fraction
720	Longest Word in Dictionary	Easy	False	False	Hash Table, Trie	Longest Word in Dictionary through Deleting, Implement Magic Dictionary
721	Accounts Merge	Medium	False	False	Depth-first Search, Union Find	Redundant Connection, Sentence Similarity, Sentence Similarity II
722	Remove Comments	Medium	False	False	String	Mini Parser, Ternary Expression Parser
723	Candy Crush	Medium	True	False	Array, Two Pointers
724	Find Pivot Index	Easy	False	False	Array	Subarray Sum Equals K
725	Split Linked List in Parts	Medium	False	False	Linked List	Rotate List, Odd Even Linked List
726	Number of Atoms	Hard	False	False	Hash Table, Stack, Recursion	Decode String, Encode String with Shortest Length, Parse Lisp Expression
727	Minimum Window Subsequence	Hard	True	False	Dynamic Programming, Sliding Window	Minimum Window Substring, Longest Continuous Increasing Subsequence
728	Self Dividing Numbers	Easy	False	False	Math	Perfect Number
729	My Calendar I	Medium	False	False	Array	My Calendar II, My Calendar III
730	Count Different Palindromic Subsequences	Hard	False	False	String, Dynamic Programming	Longest Palindromic Subsequence
731	My Calendar II	Medium	False	False	Ordered Map	My Calendar I, My Calendar III
732	My Calendar III	Hard	False	False	Segment Tree, Ordered Map	My Calendar I, My Calendar II
733	Flood Fill	Easy	False	False	Depth-first Search	Island Perimeter
734	Sentence Similarity	Easy	True	False	Hash Table	Friend Circles, Accounts Merge, Sentence Similarity II
735	Asteroid Collision	Medium	False	False	Stack	Can Place Flowers
736	Parse Lisp Expression	Hard	False	False	String	Ternary Expression Parser, Number of Atoms, Basic Calculator IV
737	Sentence Similarity II	Medium	True	False	Depth-first Search, Union Find	Friend Circles, Accounts Merge, Sentence Similarity
738	Monotone Increasing Digits	Medium	False	False	Greedy	Remove K Digits
739	Daily Temperatures	Medium	False	False	Hash Table, Stack	Next Greater Element I
740	Delete and Earn	Medium	False	False	Dynamic Programming	House Robber
741	Cherry Pickup	Hard	False	False	Dynamic Programming	Minimum Path Sum, Dungeon Game
709	To Lower Case	Easy	False	False	String
742	Closest Leaf in a Binary Tree	Medium	True	False	Tree
743	Network Delay Time	Medium	False	False	Heap, Depth-first Search, Breadth-first Search, Graph
744	Find Smallest Letter Greater Than Target	Easy	False	False	Binary Search
745	Prefix and Suffix Search	Hard	False	False	Trie	Design Add and Search Words Data Structure
746	Min Cost Climbing Stairs	Easy	False	False	Array, Dynamic Programming	Climbing Stairs
747	Largest Number At Least Twice of Others	Easy	False	False	Array
748	Shortest Completing Word	Easy	False	False	Hash Table
749	Contain Virus	Hard	False	False	Depth-first Search
750	Number Of Corner Rectangles	Medium	True	False	Dynamic Programming
751	IP to CIDR	Medium	True	False	Bit Manipulation	Restore IP Addresses, Validate IP Address
752	Open the Lock	Medium	False	False	Breadth-first Search
753	Cracking the Safe	Hard	False	False	Math, Depth-first Search
754	Reach a Number	Medium	False	False	Math
755	Pour Water	Medium	True	False	Array	Trapping Rain Water
756	Pyramid Transition Matrix	Medium	False	False	Bit Manipulation, Depth-first Search
426	Convert Binary Search Tree to Sorted Doubly Linked List	Medium	True	False	Linked List, Divide and Conquer, Tree	Binary Tree Inorder Traversal
757	Set Intersection Size At Least Two	Hard	False	False	Greedy
758	Bold Words in String	Easy	True	False	String
759	Employee Free Time	Hard	True	False	Heap, Greedy	Merge Intervals, Interval List Intersections
760	Find Anagram Mappings	Easy	True	False	Hash Table
761	Special Binary String	Hard	False	False	String, Recursion	Valid Parenthesis String
429	N-ary Tree Level Order Traversal	Medium	False	False	Tree, Breadth-first Search	Binary Tree Level Order Traversal, N-ary Tree Preorder Traversal, N-ary Tree Postorder Traversal
428	Serialize and Deserialize N-ary Tree	Hard	True	False	Tree	Serialize and Deserialize Binary Tree, Serialize and Deserialize BST, Encode N-ary Tree to Binary Tree
430	Flatten a Multilevel Doubly Linked List	Medium	False	False	Linked List, Depth-first Search	Flatten Binary Tree to Linked List
762	Prime Number of Set Bits in Binary Representation	Easy	False	False	Bit Manipulation	Number of 1 Bits
763	Partition Labels	Medium	False	False	Two Pointers, Greedy	Merge Intervals
764	Largest Plus Sign	Medium	False	False	Dynamic Programming	Maximal Square
765	Couples Holding Hands	Hard	False	False	Greedy, Union Find, Graph	First Missing Positive, Missing Number, K-Similar Strings
431	Encode N-ary Tree to Binary Tree	Hard	True	False	Tree	Serialize and Deserialize N-ary Tree
427	Construct Quad Tree	Medium	False	False
558	Logical OR of Two Binary Grids Represented as Quad-Trees	Medium	False	False
559	Maximum Depth of N-ary Tree	Easy	False	False	Tree, Depth-first Search, Breadth-first Search	Maximum Depth of Binary Tree
589	N-ary Tree Preorder Traversal	Easy	False	False	Tree	Binary Tree Preorder Traversal, N-ary Tree Level Order Traversal, N-ary Tree Postorder Traversal
590	N-ary Tree Postorder Traversal	Easy	False	False	Tree	Binary Tree Postorder Traversal, N-ary Tree Level Order Traversal, N-ary Tree Preorder Traversal
766	Toeplitz Matrix	Easy	False	False	Array	Valid Word Square
767	Reorganize String	Medium	False	False	String, Heap, Greedy, Sort	Rearrange String k Distance Apart, Task Scheduler
768	Max Chunks To Make Sorted II	Hard	False	False	Array	Max Chunks To Make Sorted
769	Max Chunks To Make Sorted	Medium	False	False	Array	Max Chunks To Make Sorted II
770	Basic Calculator IV	Hard	False	False	Hash Table, String, Stack	Parse Lisp Expression, Basic Calculator III
771	Jewels and Stones	Easy	False	False	Hash Table
700	Search in a Binary Search Tree	Easy	False	False	Tree	Closest Binary Search Tree Value, Insert into a Binary Search Tree
701	Insert into a Binary Search Tree	Medium	False	False	Tree	Search in a Binary Search Tree
772	Basic Calculator III	Hard	True	False	String, Stack	Basic Calculator, Basic Calculator II, Basic Calculator IV
702	Search in a Sorted Array of Unknown Size	Medium	True	False	Binary Search	Binary Search, Find the Index of the Large Integer
773	Sliding Puzzle	Hard	False	False	Breadth-first Search
774	Minimize Max Distance to Gas Station	Hard	True	False	Binary Search	Koko Eating Bananas
703	Kth Largest Element in a Stream	Easy	False	False	Heap	Kth Largest Element in an Array
775	Global and Local Inversions	Medium	False	False	Array, Math
776	Split BST	Medium	True	False	Tree, Recursion	Delete Node in a BST
704	Binary Search	Easy	False	False	Binary Search	Search in a Sorted Array of Unknown Size
777	Swap Adjacent in LR String	Medium	False	False	Brainteaser
778	Swim in Rising Water	Hard	False	False	Binary Search, Heap, Depth-first Search, Union Find
779	K-th Symbol in Grammar	Medium	False	False	Recursion
780	Reaching Points	Hard	False	False	Math
781	Rabbits in Forest	Medium	False	False	Hash Table, Math
782	Transform to Chessboard	Hard	False	False	Array, Math
783	Minimum Distance Between BST Nodes	Easy	False	False	Tree, Recursion	Binary Tree Inorder Traversal
784	Letter Case Permutation	Medium	False	False	Backtracking, Bit Manipulation	Subsets, Brace Expansion
785	Is Graph Bipartite?	Medium	False	False	Depth-first Search, Breadth-first Search, Graph
786	K-th Smallest Prime Fraction	Hard	False	False	Binary Search, Heap	Kth Smallest Element in a Sorted Matrix, Kth Smallest Number in Multiplication Table, Find K-th Smallest Pair Distance
787	Cheapest Flights Within K Stops	Medium	False	False	Dynamic Programming, Heap, Breadth-first Search	Maximum Vacation Days
788	Rotated Digits	Easy	False	False	String
789	Escape The Ghosts	Medium	False	False	Math
790	Domino and Tromino Tiling	Medium	False	False	Dynamic Programming
791	Custom Sort String	Medium	False	False	String
792	Number of Matching Subsequences	Medium	False	False	Array	Is Subsequence, Shortest Way to Form String
793	Preimage Size of Factorial Zeroes Function	Hard	False	False	Binary Search	Factorial Trailing Zeroes
794	Valid Tic-Tac-Toe State	Medium	False	False	Math, Recursion	Design Tic-Tac-Toe
795	Number of Subarrays with Bounded Maximum	Medium	False	False	Array
796	Rotate String	Easy	False	False
797	All Paths From Source to Target	Medium	False	False
798	Smallest Rotation with Highest Score	Hard	False	False
799	Champagne Tower	Medium	False	False
705	Design HashSet	Easy	False	False	Hash Table, Design	Design HashMap, Design Skiplist
706	Design HashMap	Easy	False	False	Hash Table, Design	Design HashSet, Design Skiplist
800	Similar RGB Color	Easy	True	False	Math, String
801	Minimum Swaps To Make Sequences Increasing	Medium	False	False	Dynamic Programming
802	Find Eventual Safe States	Medium	False	False	Depth-first Search, Graph
803	Bricks Falling When Hit	Hard	False	False	Union Find
804	Unique Morse Code Words	Easy	False	False	String
805	Split Array With Same Average	Hard	False	False	Math
806	Number of Lines To Write String	Easy	False	False
807	Max Increase to Keep City Skyline	Medium	False	False
808	Soup Servings	Medium	False	False	Dynamic Programming
809	Expressive Words	Medium	False	False	String
810	Chalkboard XOR Game	Hard	False	False	Math
811	Subdomain Visit Count	Easy	False	False	Hash Table
812	Largest Triangle Area	Easy	False	False	Math	Largest Perimeter Triangle
813	Largest Sum of Averages	Medium	False	False	Dynamic Programming
814	Binary Tree Pruning	Medium	False	False	Tree
815	Bus Routes	Hard	False	False	Breadth-first Search
816	Ambiguous Coordinates	Medium	False	False	String
817	Linked List Components	Medium	False	False	Linked List
818	Race Car	Hard	False	False	Dynamic Programming, Heap
819	Most Common Word	Easy	False	False	String
707	Design Linked List	Medium	False	False	Linked List, Design	Design Skiplist
820	Short Encoding of Words	Medium	False	False
821	Shortest Distance to a Character	Easy	False	False
822	Card Flipping Game	Medium	False	False
823	Binary Trees With Factors	Medium	False	False
708	Insert into a Sorted Circular Linked List	Medium	True	False	Linked List	Insertion Sort List
824	Goat Latin	Easy	False	False	String
825	Friends Of Appropriate Ages	Medium	False	False	Array
826	Most Profit Assigning Work	Medium	False	False	Two Pointers
827	Making A Large Island	Hard	False	False	Depth-first Search
828	Count Unique Characters of All Substrings of a Given String	Hard	False	False	Two Pointers
829	Consecutive Numbers Sum	Hard	False	False	Math
830	Positions of Large Groups	Easy	False	False	Array
831	Masking Personal Information	Medium	False	False	String
641	Design Circular Deque	Medium	False	False	Design, Queue	Design Circular Queue
622	Design Circular Queue	Medium	False	False	Design, Queue	Design Circular Deque
832	Flipping an Image	Easy	False	False	Array
833	Find And Replace in String	Medium	False	False	String
834	Sum of Distances in Tree	Hard	False	False	Tree, Depth-first Search	Distribute Coins in Binary Tree
835	Image Overlap	Medium	False	False	Array
489	Robot Room Cleaner	Hard	True	False	Depth-first Search	Walls and Gates
836	Rectangle Overlap	Easy	False	False	Math	Rectangle Area
837	New 21 Game	Medium	False	False	Dynamic Programming
838	Push Dominoes	Medium	False	False	Two Pointers, Dynamic Programming
839	Similar String Groups	Hard	False	False	Depth-first Search, Union Find, Graph
840	Magic Squares In Grid	Easy	False	False	Array
841	Keys and Rooms	Medium	False	False	Depth-first Search, Graph
842	Split Array into Fibonacci Sequence	Medium	False	False	String, Backtracking, Greedy	Additive Number, Fibonacci Number
843	Guess the Word	Hard	False	False	Minimax
844	Backspace String Compare	Easy	False	False	Two Pointers, Stack
845	Longest Mountain in Array	Medium	False	False	Two Pointers
846	Hand of Straights	Medium	False	False	Ordered Map
847	Shortest Path Visiting All Nodes	Hard	False	False	Dynamic Programming, Breadth-first Search
848	Shifting Letters	Medium	False	False	String
849	Maximize Distance to Closest Person	Medium	False	False	Array	Exam Room
850	Rectangle Area II	Hard	False	False	Segment Tree, Line Sweep
851	Loud and Rich	Medium	False	False	Depth-first Search
852	Peak Index in a Mountain Array	Easy	False	False	Binary Search	Find Peak Element, Find in Mountain Array
853	Car Fleet	Medium	False	False	Sort
854	K-Similar Strings	Hard	False	False	Breadth-first Search, Graph	Couples Holding Hands
855	Exam Room	Medium	False	False	Ordered Map	Maximize Distance to Closest Person
856	Score of Parentheses	Medium	False	False	String, Stack
857	Minimum Cost to Hire K Workers	Hard	False	False	Heap
858	Mirror Reflection	Medium	False	False	Math
859	Buddy Strings	Easy	False	False	String
860	Lemonade Change	Easy	False	False	Greedy
861	Score After Flipping Matrix	Medium	False	False	Greedy
862	Shortest Subarray with Sum at Least K	Hard	False	False	Binary Search, Queue
863	All Nodes Distance K in Binary Tree	Medium	False	False	Tree, Depth-first Search, Breadth-first Search
710	Random Pick with Blacklist	Hard	False	False	Hash Table, Binary Search, Sort, Random	Random Pick Index, Random Pick with Weight
864	Shortest Path to Get All Keys	Hard	False	False	Heap, Breadth-first Search
865	Smallest Subtree with all the Deepest Nodes	Medium	False	False	Tree
866	Prime Palindrome	Medium	False	False	Math
867	Transpose Matrix	Easy	False	False	Array
868	Binary Gap	Easy	False	False	Math
869	Reordered Power of 2	Medium	False	False	Math
870	Advantage Shuffle	Medium	False	False	Array, Greedy
871	Minimum Number of Refueling Stops	Hard	False	False	Dynamic Programming, Heap
470	Implement Rand10() Using Rand7()	Medium	False	False	Random, Rejection Sampling
872	Leaf-Similar Trees	Easy	False	False	Tree, Depth-first Search
873	Length of Longest Fibonacci Subsequence	Medium	False	False	Array, Dynamic Programming	Fibonacci Number
874	Walking Robot Simulation	Easy	False	False	Greedy
875	Koko Eating Bananas	Medium	False	False	Binary Search	Minimize Max Distance to Gas Station
876	Middle of the Linked List	Easy	False	False	Linked List
877	Stone Game	Medium	False	False	Math, Dynamic Programming, Minimax	Stone Game V
878	Nth Magical Number	Hard	False	False	Math, Binary Search
879	Profitable Schemes	Hard	False	False	Dynamic Programming
528	Random Pick with Weight	Medium	False	False	Binary Search, Random	Random Pick Index, Random Pick with Blacklist, Random Point in Non-overlapping Rectangles
519	Random Flip Matrix	Medium	False	False	Random
497	Random Point in Non-overlapping Rectangles	Medium	False	False	Binary Search, Random	Random Pick with Weight, Generate Random Point in a Circle
478	Generate Random Point in a Circle	Medium	False	False	Math, Random, Rejection Sampling	Random Point in Non-overlapping Rectangles
880	Decoded String at Index	Medium	False	False	Stack
881	Boats to Save People	Medium	False	False	Two Pointers, Greedy
882	Reachable Nodes In Subdivided Graph	Hard	False	False	Heap
883	Projection Area of 3D Shapes	Easy	False	False	Math
884	Uncommon Words from Two Sentences	Easy	False	False	Hash Table
885	Spiral Matrix III	Medium	False	False	Math	Spiral Matrix, Spiral Matrix II
886	Possible Bipartition	Medium	False	False	Depth-first Search, Graph
887	Super Egg Drop	Hard	False	False	Math, Binary Search, Dynamic Programming
888	Fair Candy Swap	Easy	False	False	Array
889	Construct Binary Tree from Preorder and Postorder Traversal	Medium	False	False	Tree
890	Find and Replace Pattern	Medium	False	False	String
891	Sum of Subsequence Widths	Hard	False	False	Array, Math
892	Surface Area of 3D Shapes	Easy	False	False	Math, Geometry
893	Groups of Special-Equivalent Strings	Easy	False	False	String
894	All Possible Full Binary Trees	Medium	False	False	Tree, Recursion
895	Maximum Frequency Stack	Hard	False	False	Hash Table, Stack
896	Monotonic Array	Easy	False	False	Array
897	Increasing Order Search Tree	Easy	False	False	Tree, Depth-first Search
898	Bitwise ORs of Subarrays	Medium	False	False	Dynamic Programming, Bit Manipulation
899	Orderly Queue	Hard	False	False	Math, String
900	RLE Iterator	Medium	False	False	Array
901	Online Stock Span	Medium	False	False	Stack
902	Numbers At Most N Given Digit Set	Hard	False	False	Math, Dynamic Programming
903	Valid Permutations for DI Sequence	Hard	False	False	Divide and Conquer, Dynamic Programming
904	Fruit Into Baskets	Medium	False	False	Two Pointers
905	Sort Array By Parity	Easy	False	False	Array
906	Super Palindromes	Hard	False	False	Math
907	Sum of Subarray Minimums	Medium	False	False	Array, Stack
908	Smallest Range I	Easy	False	False	Math
909	Snakes and Ladders	Medium	False	False	Breadth-first Search
910	Smallest Range II	Medium	False	False	Math, Greedy
911	Online Election	Medium	False	False	Binary Search	Rank Teams by Votes
912	Sort an Array	Medium	False	False
913	Cat and Mouse	Hard	False	False	Breadth-first Search, Minimax
914	X of a Kind in a Deck of Cards	Easy	False	False	Array, Math
915	Partition Array into Disjoint Intervals	Medium	False	False	Array
916	Word Subsets	Medium	False	False	String
917	Reverse Only Letters	Easy	False	False	String
918	Maximum Sum Circular Subarray	Medium	False	False	Array
919	Complete Binary Tree Inserter	Medium	False	False	Tree
920	Number of Music Playlists	Hard	False	False	Dynamic Programming
921	Minimum Add to Make Parentheses Valid	Medium	False	False	Stack, Greedy
922	Sort Array By Parity II	Easy	False	False	Array, Sort
923	3Sum With Multiplicity	Medium	False	False	Two Pointers
924	Minimize Malware Spread	Hard	False	False	Depth-first Search, Union Find
925	Long Pressed Name	Easy	False	False	Two Pointers, String
926	Flip String to Monotone Increasing	Medium	False	False	Array
927	Three Equal Parts	Hard	False	False	Math, Binary Search, Greedy
928	Minimize Malware Spread II	Hard	False	False	Depth-first Search, Union Find, Graph
929	Unique Email Addresses	Easy	False	False	String
930	Binary Subarrays With Sum	Medium	False	False	Hash Table, Two Pointers
931	Minimum Falling Path Sum	Medium	False	False	Dynamic Programming	Minimum Falling Path Sum II
932	Beautiful Array	Medium	False	False	Divide and Conquer
933	Number of Recent Calls	Easy	False	False	Queue
934	Shortest Bridge	Medium	False	False	Depth-first Search, Breadth-first Search
935	Knight Dialer	Medium	False	False	Dynamic Programming
936	Stamping The Sequence	Hard	False	False	String, Greedy
937	Reorder Data in Log Files	Easy	False	False	String
938	Range Sum of BST	Easy	False	False	Tree, Recursion
939	Minimum Area Rectangle	Medium	False	False	Hash Table
940	Distinct Subsequences II	Hard	False	False	Dynamic Programming
941	Valid Mountain Array	Easy	False	False	Array
942	DI String Match	Easy	False	False	Math
943	Find the Shortest Superstring	Hard	False	False	Dynamic Programming
944	Delete Columns to Make Sorted	Easy	False	False	Greedy
945	Minimum Increment to Make Array Unique	Medium	False	False	Array
946	Validate Stack Sequences	Medium	False	False	Stack
947	Most Stones Removed with Same Row or Column	Medium	False	False	Depth-first Search, Union Find
948	Bag of Tokens	Medium	False	False	Greedy
949	Largest Time for Given Digits	Medium	False	False	Math
950	Reveal Cards In Increasing Order	Medium	False	False	Array
951	Flip Equivalent Binary Trees	Medium	False	False	Tree
952	Largest Component Size by Common Factor	Hard	False	False	Math, Union Find
953	Verifying an Alien Dictionary	Easy	False	False	Hash Table
954	Array of Doubled Pairs	Medium	False	False	Array, Hash Table
955	Delete Columns to Make Sorted II	Medium	False	False	Greedy
956	Tallest Billboard	Hard	False	False	Dynamic Programming
957	Prison Cells After N Days	Medium	False	False	Hash Table
958	Check Completeness of a Binary Tree	Medium	False	False	Tree
959	Regions Cut By Slashes	Medium	False	False	Depth-first Search, Union Find, Graph
960	Delete Columns to Make Sorted III	Hard	False	False	Dynamic Programming
961	N-Repeated Element in Size 2N Array	Easy	False	False	Hash Table
962	Maximum Width Ramp	Medium	False	False	Array
963	Minimum Area Rectangle II	Medium	False	False	Math, Geometry
964	Least Operators to Express Number	Hard	False	False	Math, Dynamic Programming
965	Univalued Binary Tree	Easy	False	False	Tree	Find All The Lonely Nodes
966	Vowel Spellchecker	Medium	False	False	Hash Table, String
967	Numbers With Same Consecutive Differences	Medium	False	False	Depth-first Search, Breadth-first Search
968	Binary Tree Cameras	Hard	False	False	Dynamic Programming, Tree, Depth-first Search	Distribute Coins in Binary Tree
969	Pancake Sorting	Medium	False	False	Array, Sort
970	Powerful Integers	Easy	False	False	Hash Table, Math
971	Flip Binary Tree To Match Preorder Traversal	Medium	False	False	Tree, Depth-first Search
972	Equal Rational Numbers	Hard	False	False	Math
509	Fibonacci Number	Easy	False	False	Array	Climbing Stairs, Split Array into Fibonacci Sequence, Length of Longest Fibonacci Subsequence, N-th Tribonacci Number
973	K Closest Points to Origin	Medium	False	False	Divide and Conquer, Heap, Sort	Kth Largest Element in an Array, Top K Frequent Elements, Top K Frequent Words
974	Subarray Sums Divisible by K	Medium	False	False	Array, Hash Table	Subarray Sum Equals K
975	Odd Even Jump	Hard	False	False	Dynamic Programming, Stack, Ordered Map
976	Largest Perimeter Triangle	Easy	False	False	Math, Sort	Largest Triangle Area
977	Squares of a Sorted Array	Easy	False	False	Array, Two Pointers	Merge Sorted Array, Sort Transformed Array
978	Longest Turbulent Subarray	Medium	False	False	Array, Dynamic Programming, Sliding Window	Maximum Subarray
979	Distribute Coins in Binary Tree	Medium	False	False	Tree, Depth-first Search	Sum of Distances in Tree, Binary Tree Cameras
980	Unique Paths III	Hard	False	False	Backtracking, Depth-first Search	Sudoku Solver, Unique Paths II, Word Search II
981	Time Based Key-Value Store	Medium	False	False	Hash Table, Binary Search
982	Triples with Bitwise AND Equal To Zero	Hard	False	False	Dynamic Programming
983	Minimum Cost For Tickets	Medium	False	False	Dynamic Programming	Coin Change
984	String Without AAA or BBB	Medium	False	False	Greedy
985	Sum of Even Numbers After Queries	Easy	False	False	Array
986	Interval List Intersections	Medium	False	False	Two Pointers	Merge Intervals, Merge Sorted Array, Employee Free Time
987	Vertical Order Traversal of a Binary Tree	Medium	False	False	Hash Table, Tree
988	Smallest String Starting From Leaf	Medium	False	False	Tree, Depth-first Search	Sum Root to Leaf Numbers, Binary Tree Paths
989	Add to Array-Form of Integer	Easy	False	False	Array	Add Two Numbers, Plus One, Add Binary, Add Strings
990	Satisfiability of Equality Equations	Medium	False	False	Union Find, Graph
991	Broken Calculator	Medium	False	False	Math, Greedy	2 Keys Keyboard
992	Subarrays with K Different Integers	Hard	False	False	Hash Table, Two Pointers, Sliding Window	Longest Substring Without Repeating Characters, Longest Substring with At Most Two Distinct Characters, Longest Substring with At Most K Distinct Characters
993	Cousins in Binary Tree	Easy	False	False	Tree, Breadth-first Search	Binary Tree Level Order Traversal
994	Rotting Oranges	Medium	False	False	Breadth-first Search	Walls and Gates
995	Minimum Number of K Consecutive Bit Flips	Hard	False	False	Greedy, Sliding Window	Bulb Switcher
996	Number of Squareful Arrays	Hard	False	False	Math, Backtracking, Graph	Permutations II
997	Find the Town Judge	Easy	False	False	Graph	Find the Celebrity
998	Maximum Binary Tree II	Medium	False	False	Tree	Maximum Binary Tree
999	Available Captures for Rook	Easy	False	False	Array
1000	Minimum Cost to Merge Stones	Hard	False	False	Dynamic Programming	Burst Balloons, Minimum Cost to Connect Sticks
1001	Grid Illumination	Hard	False	False	Hash Table	N-Queens
1002	Find Common Characters	Easy	False	False	Array, Hash Table	Intersection of Two Arrays II
1003	Check If Word Is Valid After Substitutions	Medium	False	False	String, Stack	Valid Parentheses
1004	Max Consecutive Ones III	Medium	False	False	Two Pointers, Sliding Window	Longest Substring with At Most K Distinct Characters, Longest Repeating Character Replacement, Max Consecutive Ones, Max Consecutive Ones II
1005	Maximize Sum Of Array After K Negations	Easy	False	False	Greedy
1006	Clumsy Factorial	Medium	False	False	Math
1007	Minimum Domino Rotations For Equal Row	Medium	False	False	Array, Greedy
1008	Construct Binary Search Tree from Preorder Traversal	Medium	False	False	Tree
1055	Shortest Way to Form String	Medium	True	False	Dynamic Programming, Greedy	Is Subsequence, Number of Matching Subsequences
1057	Campus Bikes	Medium	True	False	Greedy, Sort	Campus Bikes II
1058	Minimize Rounding Error to Meet Target	Medium	True	False	Math, Dynamic Programming, Greedy
1009	Complement of Base 10 Integer	Easy	False	False	Math
1010	Pairs of Songs With Total Durations Divisible by 60	Easy	False	False	Array
1011	Capacity To Ship Packages Within D Days	Medium	False	False	Array, Binary Search
1012	Numbers With Repeated Digits	Hard	False	False	Math, Dynamic Programming
1061	Lexicographically Smallest Equivalent String	Medium	True	False	Depth-first Search, Union Find
1060	Missing Element in Sorted Array	Medium	True	False	Binary Search
1062	Longest Repeating Substring	Medium	True	False	String
1063	Number of Valid Subarrays	Hard	True	False	Stack
1013	Partition Array Into Three Parts With Equal Sum	Easy	False	False	Array
1014	Best Sightseeing Pair	Medium	False	False	Array
1015	Smallest Integer Divisible by K	Medium	False	False	Math
1016	Binary String With Substrings Representing 1 To N	Medium	False	False	String
1064	Fixed Point	Easy	True	False	Array, Binary Search
1066	Campus Bikes II	Medium	True	False	Dynamic Programming, Backtracking	Campus Bikes
1067	Digit Count in Range	Hard	True	False	Math, Dynamic Programming	Number of Digit One
1056	Confusing Number	Easy	True	False	Math	Strobogrammatic Number, Confusing Number II
1017	Convert to Base -2	Medium	False	False	Math	Encode Number
1018	Binary Prefix Divisible By 5	Easy	False	False	Array
1019	Next Greater Node In Linked List	Medium	False	False	Linked List, Stack
1020	Number of Enclaves	Medium	False	False	Depth-first Search
1086	High Five	Easy	True	False	Array, Hash Table, Sort
1065	Index Pairs of a String	Easy	True	False	String, Trie
1087	Brace Expansion	Medium	True	False	Backtracking	Decode String, Letter Case Permutation, Brace Expansion II
1088	Confusing Number II	Hard	True	False	Math, Backtracking	Confusing Number
1021	Remove Outermost Parentheses	Easy	False	False	Stack
1022	Sum of Root To Leaf Binary Numbers	Easy	False	False	Tree
1023	Camelcase Matching	Medium	False	False	String, Trie
1024	Video Stitching	Medium	False	False	Dynamic Programming
1085	Sum of Digits in the Minimum Number	Easy	True	False	Array	Add Digits
1099	Two Sum Less Than K	Easy	True	False	Array	Two Sum, Two Sum II - Input array is sorted, 3Sum Smaller, Subarray Product Less Than K
1100	Find K-Length Substrings With No Repeated Characters	Medium	True	False	String, Sliding Window
1101	The Earliest Moment When Everyone Become Friends	Medium	True	False	Union Find	Friend Circles
1025	Divisor Game	Easy	False	False	Math, Dynamic Programming
1027	Longest Arithmetic Subsequence	Medium	False	False	Dynamic Programming
1118	Number of Days in a Month	Easy	True	False
1119	Remove Vowels from a String	Easy	True	False	String	Reverse Vowels of a String
1134	Armstrong Number	Easy	True	False	Math
1120	Maximum Average Subtree	Medium	True	False	Tree
1026	Maximum Difference Between Node and Ancestor	Medium	False	False	Tree, Depth-first Search
1028	Recover a Tree From Preorder Traversal	Hard	False	False	Tree, Depth-first Search
1030	Matrix Cells in Distance Order	Easy	False	False	Sort
1029	Two City Scheduling	Medium	False	False	Greedy
1031	Maximum Sum of Two Non-Overlapping Subarrays	Medium	False	False	Array
1032	Stream of Characters	Hard	False	False	Trie
1133	Largest Unique Number	Easy	True	False	Array, Hash Table
1102	Path With Maximum Minimum Value	Medium	True	False	Depth-first Search, Union Find, Graph
1135	Connecting Cities With Minimum Cost	Medium	True	False	Union Find, Graph
1136	Parallel Courses	Hard	True	False	Dynamic Programming, Depth-first Search, Graph
1150	Check If a Number Is Majority Element in a Sorted Array	Easy	True	False	Array, Binary Search	Majority Element, Majority Element II
1033	Moving Stones Until Consecutive	Easy	False	False	Brainteaser
1034	Coloring A Border	Medium	False	False	Depth-first Search	Island Perimeter
1035	Uncrossed Lines	Medium	False	False	Array	Edit Distance
1036	Escape a Large Maze	Hard	False	False	Breadth-first Search
1151	Minimum Swaps to Group All 1's Together	Medium	True	False	Array, Sliding Window
1152	Analyze User Website Visit Pattern	Medium	True	False	Array, Hash Table, Sort
1039	Minimum Score Triangulation of Polygon	Medium	False	False	Dynamic Programming
1160	Find Words That Can Be Formed by Characters	Easy	False	False	Array, Hash Table
1040	Moving Stones Until Consecutive II	Medium	False	False	Array, Sliding Window
1038	Binary Search Tree to Greater Sum Tree	Medium	False	False	Binary Search Tree
1037	Valid Boomerang	Easy	False	False	Math
1161	Maximum Level Sum of a Binary Tree	Medium	False	False	Graph
1162	As Far from Land as Possible	Medium	False	False	Breadth-first Search, Graph	Shortest Distance from All Buildings
1121	Divide Array Into Increasing Sequences	Hard	True	False	Math
1041	Robot Bounded In Circle	Medium	False	False	Math
1042	Flower Planting With No Adjacent	Easy	False	False	Graph
1043	Partition Array for Maximum Sum	Medium	False	False	Dynamic Programming
1044	Longest Duplicate Substring	Hard	False	False	Hash Table, Binary Search
1165	Single-Row Keyboard	Easy	True	False	String
1153	String Transforms Into Another String	Hard	True	False	Graph
1166	Design File System	Medium	True	False	Hash Table, Design
1167	Minimum Cost to Connect Sticks	Medium	True	False	Greedy	Minimum Cost to Merge Stones
1046	Last Stone Weight	Easy	False	False	Heap, Greedy
1047	Remove All Adjacent Duplicates In String	Easy	False	False	Stack	Remove All Adjacent Duplicates in String II
1048	Longest String Chain	Medium	False	False	Hash Table, Dynamic Programming
1049	Last Stone Weight II	Medium	False	False	Dynamic Programming
1180	Count Substrings with Only One Distinct Letter	Easy	True	False	Math, String
1181	Before and After Puzzle	Medium	True	False	String
1163	Last Substring in Lexicographical Order	Hard	False	False	String, Suffix Array
1182	Shortest Distance to Target Color	Medium	True	False	Binary Search
1045	Customers Who Bought All Products	Medium	True	False
1050	Actors and Directors Who Cooperated At Least Three Times	Easy	True	False
1051	Height Checker	Easy	False	False	Array
1052	Grumpy Bookstore Owner	Medium	False	False	Array, Sliding Window
1053	Previous Permutation With One Swap	Medium	False	False	Array, Greedy
1054	Distant Barcodes	Medium	False	False	Heap, Sort
1196	How Many Apples Can You Put into the Basket	Easy	True	False	Greedy
1197	Minimum Knight Moves	Medium	True	False	Breadth-first Search
1198	Find Smallest Common Element in All Rows	Medium	True	False	Hash Table, Binary Search
1168	Optimize Water Distribution in a Village	Hard	True	False	Union Find, Graph
1074	Number of Submatrices That Sum to Target	Hard	False	False	Array, Dynamic Programming, Sliding Window
1071	Greatest Common Divisor of Strings	Easy	False	False	String
1072	Flip Columns For Maximum Number of Equal Rows	Medium	False	False	Hash Table
1073	Adding Two Negabinary Numbers	Medium	False	False	Math
1213	Intersection of Three Sorted Arrays	Easy	True	False	Hash Table, Two Pointers	Intersection of Two Arrays
1214	Two Sum BSTs	Medium	True	False	Binary Search Tree	Two Sum IV - Input is a BST
1215	Stepping Numbers	Medium	True	False	Backtracking
1183	Maximum Number of Ones	Hard	True	False	Math, Sort
1068	Product Sales Analysis I	Easy	True	False		Product Sales Analysis II
1069	Product Sales Analysis II	Easy	True	False		Product Sales Analysis I, Product Sales Analysis III
1070	Product Sales Analysis III	Medium	True	False		Product Sales Analysis II
1078	Occurrences After Bigram	Easy	False	False	Hash Table
1080	Insufficient Nodes in Root to Leaf Paths	Medium	False	False	Depth-first Search
1081	Smallest Subsequence of Distinct Characters	Medium	False	False	String
1079	Letter Tile Possibilities	Medium	False	False	Backtracking
1075	Project Employees I	Easy	True	False		Project Employees II
1076	Project Employees II	Easy	True	False		Project Employees I, Project Employees III
1077	Project Employees III	Medium	True	False		Project Employees II
1228	Missing Number In Arithmetic Progression	Easy	True	False	Math
1229	Meeting Scheduler	Medium	True	False	Line Sweep
1230	Toss Strange Coins	Medium	True	False	Math, Dynamic Programming
1199	Minimum Time to Build Blocks	Hard	True	False	Math, Dynamic Programming
1089	Duplicate Zeros	Easy	False	False	Array
1090	Largest Values From Labels	Medium	False	False	Hash Table, Greedy
1092	Shortest Common Supersequence	Hard	False	False	Dynamic Programming	Longest Common Subsequence
1091	Shortest Path in Binary Matrix	Medium	False	False	Breadth-first Search
1082	Sales Analysis I	Easy	True	False		Sales Analysis II
1083	Sales Analysis II	Easy	True	False		Sales Analysis I, Sales Analysis III
1084	Sales Analysis III	Easy	True	False		Sales Analysis II
1243	Array Transformation	Easy	True	False	Array
1244	Design A Leaderboard	Medium	True	False	Hash Table, Sort, Design
1245	Tree Diameter	Medium	True	False	Tree, Depth-first Search, Breadth-first Search
1216	Valid Palindrome III	Hard	True	False	String, Dynamic Programming
511	Game Play Analysis I	Easy	True	False		Game Play Analysis II
512	Game Play Analysis II	Easy	True	False		Game Play Analysis I, Game Play Analysis III
534	Game Play Analysis III	Medium	True	False		Game Play Analysis II, Game Play Analysis IV
550	Game Play Analysis IV	Medium	True	False		Game Play Analysis III, Game Play Analysis V
1093	Statistics from a Large Sample	Medium	False	False	Math, Two Pointers
1094	Car Pooling	Medium	False	False	Greedy	Meeting Rooms II
1095	Find in Mountain Array	Hard	False	False	Binary Search	Peak Index in a Mountain Array
1117	Building H2O	Medium	False	False
1115	Print FooBar Alternately	Medium	False	False		Print in Order, Print Zero Even Odd
1096	Brace Expansion II	Hard	False	False	String	Brace Expansion
1256	Encode Number	Medium	True	False	Math, Bit Manipulation	Convert to Base -2
1257	Smallest Common Region	Medium	True	False	Tree	Lowest Common Ancestor of a Binary Search Tree, Lowest Common Ancestor of a Binary Tree
1258	Synonymous Sentences	Medium	True	False	Backtracking
1231	Divide Chocolate	Hard	True	False	Binary Search, Greedy
1097	Game Play Analysis V	Hard	True	False		Game Play Analysis IV
1104	Path In Zigzag Labelled Binary Tree	Medium	False	False	Math, Tree
1103	Distribute Candies to People	Easy	False	False	Math
1105	Filling Bookcase Shelves	Medium	False	False	Dynamic Programming
1106	Parsing A Boolean Expression	Hard	False	False	String
1098	Unpopular Books	Medium	True	False
1271	Hexspeak	Easy	True	False	Math, String
1272	Remove Interval	Medium	True	False	Math, Line Sweep
1273	Delete Tree Nodes	Medium	True	False	Dynamic Programming, Depth-first Search
1246	Palindrome Removal	Hard	True	False	Dynamic Programming
1114	Print in Order	Easy	False	False		Print FooBar Alternately
1107	New Users Daily Count	Medium	True	False
1108	Defanging an IP Address	Easy	False	False	String
1109	Corporate Flight Bookings	Medium	False	False	Array, Math
1110	Delete Nodes And Return Forest	Medium	False	False	Tree, Depth-first Search
1111	Maximum Nesting Depth of Two Valid Parentheses Strings	Medium	False	False	Binary Search, Greedy
1188	Design Bounded Blocking Queue	Medium	True	False
1286	Iterator for Combination	Medium	False	False	Backtracking, Design
1291	Sequential Digits	Medium	False	False	Backtracking
1259	Handshakes That Don't Cross	Hard	True	False	Math, Dynamic Programming
1112	Highest Grade For Each Student	Medium	True	False		Department Highest Salary
1113	Reported Posts	Easy	True	False
1116	Print Zero Even Odd	Medium	False	False		Print FooBar Alternately, Fizz Buzz Multithreaded
1122	Relative Sort Array	Easy	False	False	Array, Sort
1123	Lowest Common Ancestor of Deepest Leaves	Medium	False	False	Tree, Depth-first Search
1124	Longest Well-Performing Interval	Medium	False	False	Stack
1125	Smallest Sufficient Team	Hard	False	False	Dynamic Programming, Bit Manipulation
1287	Element Appearing More Than 25% In Sorted Array	Easy	False	False	Array
1288	Remove Covered Intervals	Medium	False	False	Line Sweep
1289	Minimum Falling Path Sum II	Hard	False	False	Dynamic Programming	Minimum Falling Path Sum
1126	Active Businesses	Medium	True	False
1127	User Purchase Platform	Hard	True	False
1128	Number of Equivalent Domino Pairs	Easy	False	False	Array
1130	Minimum Cost Tree From Leaf Values	Medium	False	False	Dynamic Programming, Stack, Tree
1129	Shortest Path with Alternating Colors	Medium	False	False	Breadth-first Search, Graph
1131	Maximum of Absolute Value Expression	Medium	False	False	Math, Bit Manipulation
1299	Replace Elements with Greatest Element on Right Side	Easy	False	False	Array
1300	Sum of Mutated Array Closest to Target	Medium	False	False	Array, Binary Search
1274	Number of Ships in a Rectangle	Hard	True	False	Divide and Conquer
1301	Number of Paths with Max Score	Hard	False	False	Dynamic Programming
1137	N-th Tribonacci Number	Easy	False	False	Recursion	Climbing Stairs, Fibonacci Number
1132	Reported Posts II	Medium	True	False
1138	Alphabet Board Path	Medium	False	False	Hash Table, String
1139	Largest 1-Bordered Square	Medium	False	False	Dynamic Programming
1140	Stone Game II	Medium	False	False	Dynamic Programming	Stone Game V
1313	Decompress Run-Length Encoded List	Easy	False	False	Array	String Compression
1314	Matrix Block Sum	Medium	False	False	Dynamic Programming
1315	Sum of Nodes with Even-Valued Grandparent	Medium	False	False	Tree, Depth-first Search
1316	Distinct Echo Substrings	Hard	False	False	String, Rolling Hash
1141	User Activity for the Past 30 Days I	Easy	True	False
1142	User Activity for the Past 30 Days II	Easy	True	False
1144	Decrease Elements To Make Array Zigzag	Medium	False	False	Array
1145	Binary Tree Coloring Game	Medium	False	False	Tree, Depth-first Search
1146	Snapshot Array	Medium	False	False	Array