LeetCode Accepted Solutions

This repository contains accepted solutions of many problems from leetcode including related discussions if exists, coded in different programming languages.

Each problem has its own separate README with related explanations and examples for further reading (including ones to leetcode problem).

Read source-code by Programming Languages: Java, C#, Python, JavaScript, TypeScript

☝ Note that this project is meant to be used for learning and researching purposes only, and it is not meant to be used for production.

Table of Contents

• Folder Structure
• Contents
  • Algorithms
  • Database
  • Shell
  • JavaScript
  • Concurrency
• Algorithms
• JavaScript
• Database
• Shell
• Concurrency
• Useful Information
  • References
  • Big O Notation
  • Data Structure Operations Complexity
  • Array Sorting Algorithms Complexity
• Contributing
• License
• Author

‼️ Folder Structure

Here is the folder structure.

leetcode/
|- algorithms/
|- concurrency/
|- database/
|- javascript/
|- shell/
  ALL FOLDERS ABOVE IN-STRUCTURE IS:
    |-- {problem}/
      |-- Solution.{...}
      |-- README.md

ℹ️ Contents

Algorithms

• Bit Manipulation
• Array
• String
• Linked List
• Doubly Linked List
• Stack
• Monotonic Stack
• Monotonic Queue
• Queue
• Tree
• Hash Table
• Math
• Two Pointers
• Recursion
• Binary Search
• Binary Tree
• Breadth-First Search
• Depth-First Search
• Backtracking
• Dynamic Programming
• Divide and Conquer
• Memoization
• Greedy
• Graph
• Heap (Priority Queue)
• Quickselect
• Shortest Path
• Geometry
• Simulation
• Design
• Brainteaser
• Game Theory
• Sorting
• Prefix Sum
• Sliding Window
• Data Stream
• Concurrency
• Combinatorics
• Counting
• Union Find
• Topological Sort
• Bucket Sort
• Merge Sort

Database

• SQL

Shell

• Shell Script

JavaScript

• JS

Concurrency

• Concurrency

(back to top)

🚀 Algorithms

Bit Manipulation

#	Title	Solution	Time	Space	Difficulty	Note
67	Add Binary	Java	N/A	N/A
78	Subsets	Java	N/A	N/A
136	Single Number	Java	N/A	N/A
190	Reverse Bits	Java	N/A	N/A
191	Number of 1 Bits	Java	N/A	N/A
231	Power of Two	Java	N/A	N/A
268	Missing Number	Java	N/A	N/A
287	Find the Duplicate Number	Java	N/A	N/A
338	Counting Bits	Java	N/A	N/A
342	Power of Four	Java	N/A	N/A
389	Find the Difference	Java	N/A	N/A
784	Letter Case Permutation	Java	O(2^n)	O(2^n)		View discussion on leetcode
1318	Minimum Flips to Make a OR b Equal to c	Java	N/A	N/A
1342	Number of Steps to Reduce a Number to Zero	Java	N/A	N/A
1863	Sum of All Subset XOR Totals	Java	N/A	N/A

Backtracking

#	Title	Solution	Time	Space	Difficulty	Note
17	Letter Combinations of a Phone Number	Java	N/A	N/A
22	Generate Parentheses	Java	N/A	N/A
37	Sudoku Solver	Java	N/A	N/A
39	Combination Sum	Java	N/A	N/A
51	N-Queens	Java	N/A	N/A
77	Combinations	Java	N/A	N/A
78	Subsets	Java	N/A	N/A
79	Word Search	Java	N/A	N/A
131	Palindrome Partitioning	Java	N/A	N/A
216	Combination Sum III	Java	N/A	N/A
257	Binary Tree Paths	Java	N/A	N/A
784	Letter Case Permutation	Java	O(2^n)	O(2^n)		View discussion on leetcode
1863	Sum of All Subset XOR Totals	Java	N/A	N/A

Design

#	Title	Solution	Time	Space	Difficulty	Note
146	LRU Cache	Java	N/A	N/A
155	Min Stack	Java	N/A	N/A
208	Implement Trie (Prefix Tree)	Java	N/A	N/A
225	Implement Stack using Queues	Java	N/A	N/A
232	Implement Queue using Stacks	Java	N/A	N/A
295	Find Median from Data Stream	Java	N/A	N/A
901	Online Stock Span	Java	N/A	N/A
933	Number of Recent Calls	Java	N/A	N/A
2336	Smallest Number in Infinite Set	Java	N/A	N/A

Queue

#	Title	Solution	Time	Space	Difficulty	Note
225	Implement Stack using Queues	Java	N/A	N/A
232	Implement Queue using Stacks	Java	N/A	N/A
239	Sliding Window Maximum	Java	O(n)	O(k)
387	First Unique Character in a String	Java	N/A	N/A
649	Dota2 Senate	Java	N/A	N/A
933	Number of Recent Calls	Java	N/A	N/A

Stack

#	Title	Solution	Time	Space	Difficulty	Note
20	Valid Parentheses	Java	N/A	N/A
32	Longest Valid Parentheses	Java	N/A	N/A
42	Trapping Rain Water	Java	N/A	N/A
84	Largest Rectangle in Histogram	Java	N/A	N/A
94	Binary Tree Inorder Traversal	Java	N/A	N/A
114	Flatten Binary Tree to Linked List	Java	N/A	N/A
144	Binary Tree Preorder Traversal	Java	N/A	N/A
145	Binary Tree Postorder Traversal	Java	N/A	N/A
155	Min Stack	Java	N/A	N/A
225	Implement Stack using Queues	Java	N/A	N/A
232	Implement Queue using Stacks	Java	N/A	N/A
234	Palindrome Linked List	Java	N/A	N/A
394	Decode String	Java	N/A	N/A
735	Asteroid Collision	Java	O(N + k)	O(N)
739	Daily Temperatures	Java	O(N)	O(N)
901	Online Stock Span	Java	N/A	N/A
2130	Leaf Similar Trees	Java	O(N)	O(N)
2390	Removing Stars From a String	Java	O(N)	O(NlogN)

Monotonic Stack

#	Title	Solution	Time	Space	Difficulty	Note
42	Trapping Rain Water	Java	N/A	N/A
84	Largest Rectangle in Histogram	Java	N/A	N/A
739	Daily Temperatures	Java	O(N)	O(N)
901	Online Stock Span	Java	N/A	N/A

Monotonic Queue

#	Title	Solution	Time	Space	Difficulty	Note
239	Sliding Window Maximum	Java	O(n)	O(k)

Brainteaser

#	Title	Solution	Time	Space	Difficulty	Note
292	Nim Game	Java	N/A	N/A

Game Theory

#	Title	Solution	Time	Space	Difficulty	Note
292	Nim Game	Java	N/A	N/A

Sorting

#	Title	Solution	Time	Space	Difficulty	Note
15	3Sum	Java	N/A	N/A
16	3Sum Closest	Java	N/A	N/A
18	4Sum	Java	N/A	N/A
49	Group Anagrams	Java	N/A	N/A
56	Merge Intervals	Java	N/A	N/A
75	Sort Colors	Java	N/A	N/A
148	Sort List	Java	N/A	N/A
169	Majority Element	Java	N/A	N/A
215	Kth Largest Element in an Array	Java	N/A	N/A
217	Contains Duplicate	Java	N/A	N/A
242	Valid Anagram	Java	N/A	N/A
268	Missing Number	Java	N/A	N/A
295	Find Median from Data Stream	Java	N/A	N/A
347	Top K Frequent Elements	Java	N/A	N/A
350	Intersection of Two Arrays II	Java	N/A	N/A
389	Find the Difference	Java	N/A	N/A
414	Third Maximum Number	Java	N/A	N/A
435	Non-overlapping Intervals	Java	N/A	N/A
452	Minimum Number of Arrows to Burst Balloons	Java	N/A	N/A
455	Assign Cookies	Java	N/A	N/A
977	Squares of a Sorted Array	Java	O(n)	O(n)		View discussion on leetcode
1337	The K Weakest Rows in a Matrix	Java	O(nlogm)	O(n)		View discussion on leetcode
1346	Check If N and Its Double Exist	Java	N/A	N/A
1385	Find the Distance Value Between Two Arrays	Java	N/A	N/A
1491	Average Salary Excluding the Minimum and Maximum Salary	Java	N/A	N/A
1608	Special Array With X Elements Greater Than or Equal X	Java	O(nlogn)	O(1)		View discussion on leetcode
1657	Determine if Two Strings Are Close	Java	O(N)	O(1)
1679	Max Number of K-Sum Pairs	Java	O(N)	O(1)
2300	Successful Pairs of Spells and Potions	Java	N/A	N/A
2542	Maximum Subsequence Score	Java	N/A	N/A

Prefix Sum

#	Title	Solution	Time	Space	Difficulty	Note
238	Product of Array Except Self	Java	O(N)	O(N)
560	Subarray Sum Equals K	Java	N/A	N/A
724	Find Pivot Index	Java	N/A	N/A
1004	Max Consecutive Ones III	Java	O(N + k)	O(1)
1480	Running Sum of 1D Array	Java	N/A	N/A
1732	Find the Highest Altitude	Java	O(N)	O(1)

Sliding Window

#	Title	Solution	Time	Space	Difficulty	Note
3	Longest Substring Without Repeating Characters	Java	N/A	N/A
76	Minimum Window Substring	Java	N/A	N/A
219	Contains Duplicate II	Java	O(N)	O(N)
239	Sliding Window Maximum	Java	O(n)	O(k)
438	Find All Anagrams in a String	Java	N/A	N/A
567	Permutation in String	Java	N/A	N/A
643	Maximum Average Subarray I	Java	O(N)	O(1)
1004	Max Consecutive Ones III	Java	O(N + k)	O(1)
1456	Maximum Number of Vowels in a Substring of Given Length	Java	O(N)	O(1)
1493	Longest Subarray of 1's After Deleting One Element	Java	O(N + k)	O(1)

Data Stream

#	Title	Solution	Time	Space	Difficulty	Note
295	Find Median from Data Stream	Java	N/A	N/A
901	Online Stock Span	Java	N/A	N/A
933	Number of Recent Calls	Java	N/A	N/A

Greedy

#	Title	Solution	Time	Space	Difficulty	Note
11	Container With Most Water	Java	N/A	N/A
45	Jump Game II	Java	N/A	N/A
334	Increasing Triplet Subsequence	Java	O(N)	O(1)
435	Non-overlapping Intervals	Java	N/A	N/A
452	Minimum Number of Arrows to Burst Balloons	Java	N/A	N/A
455	Assign Cookies	Java	N/A	N/A
605	Can Place Flowers	Java	O(N)	O(1)
649	Dota2 Senate	Java	N/A	N/A
680	Valid Palindrome II	Java	N/A	N/A
763	Partition Labels	Java	N/A	N/A
1323	Maximum 69 Number	Java	O(n)	O(n)		View discussion on leetcode
1855	Maximum Distance Between a Pair of Values	Java	N/A	N/A
2542	Maximum Subsequence Score	Java	N/A	N/A

Graph

#	Title	Solution	Time	Space	Difficulty	Note
207	Course Schedule	Java	N/A	N/A
399	Evaluate Division	Java	N/A	N/A
547	Number of Provinces	Java	N/A	N/A
841	Keys and Rooms	Java	N/A	N/A
1466	Reorder Routes to Make All Paths Lead to the City Zero	Java	O(n)	O(n)		View discussion on leetcode

Heap (Priority Queue)

#	Title	Solution	Time	Space	Difficulty	Note
23	Merge k Sorted Lists	Java	N/A	N/A
215	Kth Largest Element in an Array	Java	N/A	N/A
239	Sliding Window Maximum	Java	O(n)	O(k)
295	Find Median from Data Stream	Java	N/A	N/A
347	Top K Frequent Elements	Java	N/A	N/A
1337	The K Weakest Rows in a Matrix	Java	O(nlogm)	O(n)		View discussion on leetcode
2336	Smallest Number in Infinite Set	Java	N/A	N/A
2462	Total Cost to Hire K Workers	Java	N/A	N/A
2542	Maximum Subsequence Score	Java	N/A	N/A

Quickselect

#	Title	Solution	Time	Space	Difficulty	Note
215	Kth Largest Element in an Array	Java	N/A	N/A

Shortest Path

#	Title	Solution	Time	Space	Difficulty	Note
399	Evaluate Division	Java	N/A	N/A

Matrix

#	Title	Solution	Time	Space	Difficulty	Note
36	Valid Sudoku	Java	O(n2)	O(1)		View discussion on leetcode
37	Sudoku Solver	Java	N/A	N/A
48	Rotate Image	Java	N/A	N/A
64	Minimum Path Sum	Java	N/A	N/A
73	Set Matrix Zeroes	Java	N/A	N/A
74	Search a 2D Matrix	Java	N/A	N/A		View discussion on leetcode
79	Word Search	Java	N/A	N/A
200	Number of Islands	Java	N/A	N/A
240	Search a 2D Matrix II	Java	N/A	N/A
542	01 Matrix	Java	O(nm)	O(nm)		View discussion on leetcode
695	Max Area of Island	Java	N/A	N/A
733	Flood Fill	Java	N/A	N/A
867	Transpose Matrix	Java	N/A	N/A
994	Rotting Oranges	Java	N/A	N/A
1337	The K Weakest Rows in a Matrix	Java	O(nlogm)	O(n)		View discussion on leetcode
1351	Count Negative Numbers in a Sorted Matrix	Java	N/A	N/A
1572	Matrix Diagonal Sum	Java	O(n)	O(1)		View discussion on leetcode
1672	Richest Customer Wealth	Java	N/A	N/A
2352	Equal Row and Column Pairs	Java	O(N^3)	O(1)
1926	Nearest Exit from Entrance in Maze	Java	N/A	N/A

Simulation

#	Title	Solution	Time	Space	Difficulty	Note
67	Add Binary	Java	N/A	N/A
258	Add Digits	Java	N/A	N/A
412	Fizz Buzz	Java	N/A	N/A
867	Transpose Matrix	Java	N/A	N/A
2352	Equal Row and Column Pairs	Java	O(N^3)	O(1)
2390	Removing Stars From a String	Java	O(N)	O(NlogN)
2462	Total Cost to Hire K Workers	Java	N/A	N/A
2660	Determine the Winner of a Bowling Game	Java, Python, JavaScript	O(n)	O(1)		View discussion on leetcode

Dynamic Programming

#	Title	Solution	Time	Space	Difficulty	Note
5	Longest Palindromic Substring	Java	N/A	N/A
22	Generate Parentheses	Java	N/A	N/A
32	Longest Valid Parentheses	Java	N/A	N/A
42	Trapping Rain Water	Java	N/A	N/A
45	Jump Game II	Java	N/A	N/A
53	Maximum Subarray	Java	N/A	N/A
62	Unique Paths	Java	N/A	N/A		View discussion on leetcode
64	Minimum Path Sum	Java	N/A	N/A
70	Climbing Stairs	Java	N/A	N/A
72	Edit Distance	Java	N/A	N/A
121	Best Time to Buy and Sell Stock	Java	N/A	N/A
118	Pascal's Triangle	Java	O(n^2)	O(n^2)		View discussion on leetcode
119	Pascal's Triangle II	Java	O(n)	O(n)		View discussion on leetcode
121	Best Time to Buy and Sell Stock	Java	N/A	N/A
124	Binary Tree Maximum Path Sum	Java	N/A	N/A
131	Palindrome Partitioning	Java	N/A	N/A
139	Word Break	Java	N/A	N/A
152	Maximum Product Subarray	Java	N/A	N/A
198	House Robber	Java	O(N)	O(N)
279	Perfect Squares	Java	N/A	N/A
300	Longest Increasing Subsequence	Java	N/A	N/A
322	Coin Change	Java	N/A	N/A
338	Counting Bits	Java	N/A	N/A
392	Is Subsequence	Java	N/A	N/A
416	Partition Equal Subset Sum	Java	N/A	N/A
435	Non-overlapping Intervals	Java	N/A	N/A
542	01 Matrix	Java	O(nm)	O(nm)		View discussion on leetcode
746	Min Cost Climbing Stairs	Java	N/A	N/A
790	Domino and Tromino Tiling	Java	N/A	N/A
1137	N-th Tribonacci Number	Java	N/A	N/A
1143	Longest Common Subsequence	Java	N/A	N/A
1372	Longest ZigZag Path in a Binary Tree	Java	N/A	N/A
1493	Longest Subarray of 1's After Deleting One Element	Java	O(N + k)	O(1)
1863	Sum of All Subset XOR Totals	Java	N/A	N/A

Divide and Conquer

#	Title	Solution	Time	Space	Difficulty	Note
4	Median of Two Sorted Arrays	Java	N/A	N/A
23	Merge k Sorted Lists	Java	N/A	N/A
53	Maximum Subarray	Java	N/A	N/A
105	Construct Binary Tree from Preorder and Inorder Traversal	Java	N/A	N/A
108	Convert Sorted Array to Binary Search Tree	Java	N/A	N/A
148	Sort List	Java	N/A	N/A
169	Majority Element	Java	N/A	N/A
190	Reverse Bits	Java	N/A	N/A
191	Number of 1 Bits	Java	N/A	N/A
215	Kth Largest Element in an Array	Java	N/A	N/A
240	Search a 2D Matrix II	Java	N/A	N/A
347	Top K Frequent Elements	Java	N/A	N/A

Memoization

#	Title	Solution	Time	Space	Difficulty	Note
70	Climbing Stairs	Java	N/A	N/A
139	Word Break	Java	N/A	N/A
1137	N-th Tribonacci Number	Java	N/A	N/A

Trie

#	Title	Solution	Time	Space	Difficulty	Note
14	Longest Common Prefix	Java	N/A	N/A
139	Word Break	Java	N/A	N/A
208	Implement Trie (Prefix Tree)	Java	N/A	N/A
1268	Search Suggestions System	Java	N/A	N/A

Math

#	Title	Solution	Time	Space	Difficulty	Note
2	Add Two Numbers	Java	N/A	N/A
7	Reverse Integer	Java	N/A	N/A
9	Palindrome Number	Java	N/A	N/A
12	Integer to Roman	Java	N/A	N/A
13	Roman to Integer	Java	N/A	N/A
48	Rotate Image	Java	N/A	N/A
50	Pow(x, n)	Java	N/A	N/A
62	Unique Paths	Java	N/A	N/A		View discussion on leetcode
66	Plus One	Java	N/A	N/A
67	Add Binary	Java	N/A	N/A
69	Sqrt(x)	Java	N/A	N/A
70	Climbing Stairs	Java	N/A	N/A
168	Excel Sheet Column Title	Java	N/A	N/A
171	Excel Sheet Column Title	Java	O(n)	O(1)
189	Rotate Array	Java	N/A	O(1)		View discussion on leetcode
202	Happy Number	Java	O(k∗logn)	O(k)		View discussion on leetcode
231	Power of Two	Java	N/A	N/A
258	Add Digits	Java	N/A	N/A
263	Ugly Number	Java	N/A	N/A
268	Missing Number	Java	N/A	N/A
279	Perfect Squares	Java	N/A	N/A
292	Nim Game	Java	N/A	N/A
326	Power of Three	Java	O(log3n)	O(log3n)		View discussion on leetcode
342	Power of Four	Java	N/A	N/A
367	Valid Perfect Square	Java	N/A	N/A
412	Fizz Buzz	Java	N/A	N/A
441	Arranging Coins	Java	O(logn)	O(1)
633	Sum of Square Numbers	Java	O(n)	O(1)
728	Self Dividing Numbers	Java	N/A	N/A
1137	N-th Tribonacci Number	Java	N/A	N/A
1323	Maximum 69 Number	Java	O(n)	O(n)		View discussion on leetcode
1342	Number of Steps to Reduce a Number to Zero	Java	N/A	N/A
1822	Sign of the Product of an Array	Java	N/A	N/A
1863	Sum of All Subset XOR Totals	Java	N/A	N/A

Tree

#	Title	Solution	Time	Space	Difficulty	Note
94	Binary Tree Inorder Traversal	Java	N/A	N/A
98	Validate Binary Search Tree	Java	N/A	N/A
100	Same Tree	Java	N/A	N/A
101	Symmetric Tree	Java	N/A	N/A
102	Valid Anagram	Java	N/A	N/A
104	Maximum Depth of Binary Tree	Java	N/A	N/A
105	Construct Binary Tree from Preorder and Inorder Traversal	Java	N/A	N/A
108	Convert Sorted Array to Binary Search Tree	Java	N/A	N/A
110	Balanced Binary Tree	Java	N/A	N/A
111	Minimum Depth of Binary Tree	Java	N/A	N/A
114	Flatten Binary Tree to Linked List	Java	N/A	N/A
116	Populating Next Right Pointers in Each Node	Java	N/A	N/A
124	Binary Tree Maximum Path Sum	Java	N/A	N/A
144	Binary Tree Preorder Traversal	Java	N/A	N/A
145	Binary Tree Postorder Traversal	Java	N/A	N/A
199	Binary Tree Right Side View	Java	N/A	N/A
226	Invert Binary Tree	Java	N/A	N/A
230	Kth Smallest Element in a BST	Java	N/A	N/A
235	Lowest Common Ancestor of a Binary Search Tree	Java	O(logn)	O(logn)		View discussion on leetcode
236	Lowest Common Ancestor of a Binary Tree	Java	N/A	N/A
257	Binary Tree Paths	Java	N/A	N/A
404	Sum of Left Leaves	Java	N/A	N/A
437	Path Sum III	Java	N/A	N/A
450	Delete Node in a BST	Java	N/A	N/A
543	Diameter of Binary Tree	Java	N/A	N/A
617	Merge Two Binary Trees	Java	N/A	N/A
653	Two Sum IV - Input is a BST	Java	N/A	N/A
700	Search in a Binary Search Tree	Java	N/A	N/A
701	Insert into a Binary Search Tree	Java	N/A	N/A
872	Leaf Similar Trees	Java	N/A	N/A
1161	Maximum Level Sum of a Binary Tree	Java	N/A	N/A
1372	Longest ZigZag Path in a Binary Tree	Java	N/A	N/A
1448	Count Good Nodes in Binary Tree	Java	N/A	N/A

Binary Search

#	Title	Solution	Time	Space	Difficulty	Note
4	Median of Two Sorted Arrays	Java	N/A	N/A
33	Search in Rotated Sorted Array	Java	N/A	N/A
34	Find First and Last Position of Element in Sorted Array	Java	O(logn)	O(1)
35	Search Insert Position	Java	N/A	N/A		View discussion on leetcode
69	Sqrt(x)	Java	N/A	N/A
74	Search a 2D Matrix	Java	N/A	N/A		View discussion on leetcode
153	Find Minimum in Rotated Sorted Array	Java	N/A	N/A
162	Find Peak Element	Java	N/A	N/A
240	Search a 2D Matrix II	Java	N/A	N/A
268	Missing Number	Java	N/A	N/A
278	First Bad Version	Java	O(logn)	O(1)		View discussion on leetcode
287	Find the Duplicate Number	Java	N/A	N/A
300	Longest Increasing Subsequence	Java	N/A	N/A
350	Intersection of Two Arrays II	Java	N/A	N/A
367	Valid Perfect Square	Java	N/A	N/A
374	Guess Number Higher or Lower	Java	O(logn)	O(1)
441	Arranging Coins	Java	O(logn)	O(1)
450	Delete Node in a BST	Java	N/A	N/A
633	Sum of Square Numbers	Java	O(n)	O(1)
704	Binary Search	Java, Python, C#, JavaScript, TypeScript	O(logn)	O(1)
744	Find Smallest Letter Greater Than Target	Java	N/A	N/A
852	Peak Index in a Mountain Array	Java	O(logn)	O(1)
875	Koko Eating Bananas	Java	N/A	N/A
1004	Max Consecutive Ones III	Java	O(N + k)	O(1)
1337	The K Weakest Rows in a Matrix	Java	O(nlogm)	O(n)		View discussion on leetcode
1346	Check If N and Its Double Exist	Java	N/A	N/A
1351	Count Negative Numbers in a Sorted Matrix	Java	N/A	N/A
1385	Find the Distance Value Between Two Arrays	Java	N/A	N/A
1539	Kth Missing Positive Number	Java	O(logn)	O(n)
1608	Special Array With X Elements Greater Than or Equal X	Java	O(nlogn)	O(1)		View discussion on leetcode
1855	Maximum Distance Between a Pair of Values	Java	N/A	N/A
2300	Successful Pairs of Spells and Potions	Java	N/A	N/A

Binary Tree

#	Title	Solution	Time	Space	Difficulty	Note
94	Binary Tree Inorder Traversal	Java	N/A	N/A
98	Validate Binary Search Tree	Java	N/A	N/A
100	Same Tree	Java	N/A	N/A
101	Symmetric Tree	Java	N/A	N/A
102	Valid Anagram	Java	N/A	N/A
104	Maximum Depth of Binary Tree	Java	N/A	N/A
105	Construct Binary Tree from Preorder and Inorder Traversal	Java	N/A	N/A
108	Convert Sorted Array to Binary Search Tree	Java	N/A	N/A
110	Balanced Binary Tree	Java	N/A	N/A
111	Minimum Depth of Binary Tree	Java	N/A	N/A
114	Flatten Binary Tree to Linked List	Java	N/A	N/A
116	Populating Next Right Pointers in Each Node	Java	N/A	N/A
124	Binary Tree Maximum Path Sum	Java	N/A	N/A
144	Binary Tree Preorder Traversal	Java	N/A	N/A
145	Binary Tree Preorder Traversal	Java	N/A	N/A
199	Binary Tree Right Side View	Java	N/A	N/A
226	Invert Binary Tree	Java	N/A	N/A
230	Kth Smallest Element in a BST	Java	N/A	N/A
235	Lowest Common Ancestor of a Binary Search Tree	Java	O(logn)	O(logn)		View discussion on leetcode
236	Lowest Common Ancestor of a Binary Tree	Java	N/A	N/A
257	Binary Tree Paths	Java	N/A	N/A
404	Sum of Left Leaves	Java	N/A	N/A
437	Path Sum III	Java	N/A	N/A
450	Delete Node in a BST	Java	N/A	N/A
543	Diameter of Binary Tree	Java	N/A	N/A
617	Merge Two Binary Trees	Java	N/A	N/A
653	Two Sum IV - Input is a BST	Java	N/A	N/A
700	Search in a Binary Search Tree	Java	N/A	N/A
701	Insert into a Binary Search Tree	Java	N/A	N/A
872	Leaf Similar Trees	Java	N/A	N/A
1161	Maximum Level Sum of a Binary Tree	Java	N/A	N/A
1372	Longest ZigZag Path in a Binary Tree	Java	N/A	N/A
1448	Count Good Nodes in Binary Tree	Java	N/A	N/A

Hash Table

#	Title	Solution	Time	Space	Difficulty	Note
1	Two Sum	Java	N/A	N/A
3	Longest Substring Without Repeating Characters	Java	N/A	N/A
12	Integer to Roman	Java	N/A	N/A
13	Roman to Integer	Java	N/A	N/A
17	Letter Combinations of a Phone Number	Java	N/A	N/A
36	Valid Sudoku	Java	O(n2)	O(1)		View discussion on leetcode
37	Sudoku Solver	Java	N/A	N/A
41	First Missing Positive	Java	N/A	N/A
49	Group Anagrams	Java	N/A	N/A
73	Set Matrix Zeroes	Java	N/A	N/A
76	Minimum Window Substring	Java	N/A	N/A
105	Construct Binary Tree from Preorder and Inorder Traversal	Java	N/A	N/A
128	Longest Consecutive Sequence	Java	N/A	N/A
138	Copy List with Random Pointer	Java	N/A	N/A
139	Word Break	Java	N/A	N/A
141	Linked List Cycle	Java	N/A	N/A
142	Linked List Cycle II	Java	N/A	N/A
146	LRU Cache	Java	N/A	N/A
160	Intersection of Two Linked Lists	Java	N/A	N/A
169	Majority Element	Java	N/A	N/A
202	Happy Number	Java	O(k∗logn)	O(k)		View discussion on leetcode
205	Isomorphic Strings	Java	O(n)	O(1)
208	Implement Trie (Prefix Tree)	Java	N/A	N/A
217	Contains Duplicate	Java	N/A	N/A
219	Contains Duplicate II	Java	O(N)	O(N)
242	Valid Anagram	Java	N/A	N/A
268	Missing Number	Java	N/A	N/A
290	Word Pattern	Java	N/A	N/A
347	Top K Frequent Elements	Java	N/A	N/A
350	Intersection of Two Arrays II	Java	N/A	N/A
383	Ransom Note	Java	N/A	N/A
387	First Unique Character in a String	Java	N/A	N/A
389	Find the Difference	Java	N/A	N/A
438	Find All Anagrams in a String	Java	N/A	N/A
560	Subarray Sum Equals K	Java	N/A	N/A
567	Permutation in String	Java	N/A	N/A
653	Two Sum IV - Input is a BST	Java	N/A	N/A
763	Partition Labels	Java	N/A	N/A
1207	Unique Number of Occurrences	Java	O(N)	O(N)
1346	Check If N and Its Double Exist	Java	N/A	N/A
1657	Determine if Two Strings Are Close	Java	O(N)	O(1)
1679	Max Number of K-Sum Pairs	Java	O(N)	O(1)
2215	Find the Difference of Two Arrays	Java	N/A	N/A
2336	Smallest Number in Infinite Set	Java	N/A	N/A
2352	Equal Row and Column Pairs	Java	O(N^3)	O(1)

Depth-First Search

#	Title	Solution	Time	Space	Difficulty	Note
94	Binary Tree Inorder Traversal	Java	N/A	N/A
98	Validate Binary Search Tree	Java	N/A	N/A
100	Same Tree	Java	N/A	N/A
101	Symmetric Tree	Java	N/A	N/A
104	Maximum Depth of Binary Tree	Java	N/A	N/A
110	Balanced Binary Tree	Java	N/A	N/A
111	Minimum Depth of Binary Tree	Java	N/A	N/A
114	Flatten Binary Tree to Linked List	Java	N/A	N/A
116	Populating Next Right Pointers in Each Node	Java	N/A	N/A
124	Binary Tree Maximum Path Sum	Java	N/A	N/A
144	Binary Tree Preorder Traversal	Java	N/A	N/A
145	Binary Tree Preorder Traversal	Java	N/A	N/A
199	Binary Tree Right Side View	Java	N/A	N/A
200	Number of Islands	Java	N/A	N/A
207	Course Schedule	Java	N/A	N/A
226	Invert Binary Tree	Java	N/A	N/A
230	Kth Smallest Element in a BST	Java	N/A	N/A
235	Lowest Common Ancestor of a Binary Search Tree	Java	O(logn)	O(logn)		View discussion on leetcode
236	Lowest Common Ancestor of a Binary Tree	Java	N/A	N/A
257	Binary Tree Paths	Java	N/A	N/A
399	Evaluate Division	Java	N/A	N/A
404	Sum of Left Leaves	Java	N/A	N/A
437	Path Sum III	Java	N/A	N/A
543	Diameter of Binary Tree	Java	N/A	N/A
547	Number of Provinces	Java	N/A	N/A
617	Merge Two Binary Trees	Java	N/A	N/A
653	Two Sum IV - Input is a BST	Java	N/A	N/A
695	Max Area of Island	Java	N/A	N/A
733	Flood Fill	Java	N/A	N/A
841	Keys and Rooms	Java	N/A	N/A
872	Leaf Similar Trees	Java	N/A	N/A
1161	Maximum Level Sum of a Binary Tree	Java	N/A	N/A
1372	Longest ZigZag Path in a Binary Tree	Java	N/A	N/A
1448	Count Good Nodes in Binary Tree	Java	N/A	N/A
1466	Reorder Routes to Make All Paths Lead to the City Zero	Java	O(n)	O(n)		View discussion on leetcode

Breadth-First Search

#	Title	Solution	Time	Space	Difficulty	Note
100	Same Tree	Java	N/A	N/A
101	Symmetric Tree	Java	N/A	N/A
102	Valid Anagram	Java	N/A	N/A
104	Maximum Depth of Binary Tree	Java	N/A	N/A
111	Minimum Depth of Binary Tree	Java	N/A	N/A
116	Populating Next Right Pointers in Each Node	Java	N/A	N/A
199	Binary Tree Right Side View	Java	N/A	N/A
200	Number of Islands	Java	N/A	N/A
207	Course Schedule	Java	N/A	N/A
226	Invert Binary Tree	Java	N/A	N/A
279	Perfect Squares	Java	N/A	N/A
322	Coin Change	Java	N/A	N/A
399	Evaluate Division	Java	N/A	N/A
404	Sum of Left Leaves	Java	N/A	N/A
542	01 Matrix	Java	O(nm)	O(nm)		View discussion on leetcode
547	Number of Provinces	Java	N/A	N/A
617	Merge Two Binary Trees	Java	N/A	N/A
653	Two Sum IV - Input is a BST	Java	N/A	N/A
695	Max Area of Island	Java	N/A	N/A
733	Flood Fill	Java	N/A	N/A
841	Keys and Rooms	Java	N/A	N/A
994	Rotting Oranges	Java	N/A	N/A
1161	Maximum Level Sum of a Binary Tree	Java	N/A	N/A
1448	Count Good Nodes in Binary Tree	Java	N/A	N/A
1466	Reorder Routes to Make All Paths Lead to the City Zero	Java	O(n)	O(n)		View discussion on leetcode
1926	Nearest Exit from Entrance in Maze	Java	N/A	N/A

Recursion

#	Title	Solution	Time	Space	Difficulty	Note
2	Add Two Numbers	Java	N/A	N/A
21	Merge Two Sorted Lists	Java	N/A	N/A
24	Swap Nodes in Pairs	Java	N/A	N/A
25	Reverse Nodes in k-Group	Java	N/A	N/A
50	Pow(x, n)	Java	N/A	N/A
203	Remove Linked List Elements	Java	N/A	N/A
206	Reverse Linked List	Java	O(n)	O(1)
231	Power of Two	Java	N/A	N/A
234	Palindrome Linked List	Java	N/A	N/A
326	Power of Three	Java	O(log3n)	O(log3n)		View discussion on leetcode
342	Power of Four	Java	N/A	N/A
394	Decode String	Java	N/A	N/A

Array

#	Title	Solution	Time	Space	Difficulty	Note
1	Two Sum	Java	N/A	N/A
4	Median of Two Sorted Arrays	Java	N/A	N/A
11	Container With Most Water	Java	N/A	N/A
15	3Sum	Java	N/A	N/A
16	3Sum Closest	Java	N/A	N/A
18	4Sum	Java	N/A	N/A
26	Remove Duplicates from Sorted Array	Java	N/A	N/A
27	Remove Element	Java	N/A	N/A
31	Next Permutation	Java	N/A	N/A
33	Search in Rotated Sorted Array	Java	N/A	N/A
34	Find First and Last Position of Element in Sorted Array	Java	O(logn)	O(1)
35	Search Insert Position	Java	N/A	N/A		View discussion on leetcode
36	Valid Sudoku	Java	O(n2)	O(1)		View discussion on leetcode
37	Sudoku Solver	Java	N/A	N/A
39	Combination Sum	Java	N/A	N/A
41	First Missing Positive	Java	N/A	N/A
42	Trapping Rain Water	Java	N/A	N/A
45	Jump Game II	Java	N/A	N/A
48	Rotate Image	Java	N/A	N/A
49	Group Anagrams	Java	N/A	N/A
51	N-Queens	Java	N/A	N/A
53	Maximum Subarray	Java	N/A	N/A
56	Merge Intervals	Java	N/A	N/A
64	Minimum Path Sum	Java	N/A	N/A
66	Plus One	Java	N/A	N/A
73	Set Matrix Zeroes	Java	N/A	N/A
74	Search a 2D Matrix	Java	N/A	N/A		View discussion on leetcode
75	Sort Colors	Java	N/A	N/A
78	Subsets	Java	N/A	N/A
79	Word Search	Java	N/A	N/A
84	Largest Rectangle in Histogram	Java	N/A	N/A
105	Construct Binary Tree from Preorder and Inorder Traversal	Java	N/A	N/A
108	Convert Sorted Array to Binary Search Tree	Java	N/A	N/A
118	Pascal's Triangle	Java	O(n^2)	O(n^2)		View discussion on leetcode
119	Pascal's Triangle II	Java	O(n)	O(n)		View discussion on leetcode
121	Best Time to Buy and Sell Stock	Java	N/A	N/A
128	Longest Consecutive Sequence	Java	N/A	N/A
136	Single Number	Java	N/A	N/A
139	Word Break	Java	N/A	N/A
152	Maximum Product Subarray	Java	N/A	N/A
153	Find Minimum in Rotated Sorted Array	Java	N/A	N/A
162	Find Peak Element	Java	N/A	N/A
167	Two Sum II - Input Array Is Sorted	Java	O(n)	O(1)		View discussion on leetcode
169	Majority Element	Java	N/A	N/A
189	Rotate Array	Java	N/A	O(1)		View discussion on leetcode
198	House Robber	Java	O(N)	O(N)
200	Number of Islands	Java	N/A	N/A
215	Kth Largest Element in an Array	Java	N/A	N/A
216	Combination Sum III	Java	N/A	N/A
217	Contains Duplicate	Java	N/A	N/A
219	Contains Duplicate II	Java	O(N)	O(N)
228	Summary Ranges	Java	N/A	N/A
238	Product of Array Except Self	Java	O(N)	O(N)
239	Sliding Window Maximum	Java	O(n)	O(k)
240	Search a 2D Matrix II	Java	N/A	N/A
268	Missing Number	Java	N/A	N/A
283	Move Zeroes	Java	O(n)	O(1)		View discussion on leetcode
287	Find the Duplicate Number	Java	N/A	N/A
300	Longest Increasing Subsequence	Java	N/A	N/A
322	Coin Change	Java	N/A	N/A
334	Increasing Triplet Subsequence	Java	O(N)	O(1)
347	Top K Frequent Elements	Java	N/A	N/A
350	Intersection of Two Arrays II	Java	N/A	N/A
399	Evaluate Division	Java	N/A	N/A
414	Third Maximum Number	Java	N/A	N/A
416	Partition Equal Subset Sum	Java	N/A	N/A
435	Non-overlapping Intervals	Java	N/A	N/A
452	Minimum Number of Arrows to Burst Balloons	Java	N/A	N/A
455	Assign Cookies	Java	N/A	N/A
542	01 Matrix	Java	O(nm)	O(nm)		View discussion on leetcode
560	Subarray Sum Equals K	Java	N/A	N/A
605	Can Place Flowers	Java	O(N)	O(1)
643	Maximum Average Subarray I	Java	O(N)	O(1)
695	Max Area of Island	Java	N/A	N/A
704	Binary Search	Java, Python, C#, JavaScript, TypeScript	O(logn)	O(1)
724	Find Pivot Index	Java	N/A	N/A
733	Flood Fill	Java	N/A	N/A
735	Asteroid Collision	Java	O(N + k)	O(N)
739	Daily Temperatures	Java	O(N)	O(N)
744	Find Smallest Letter Greater Than Target	Java	N/A	N/A
746	Min Cost Climbing Stairs	Java	N/A	N/A
852	Peak Index in a Mountain Array	Java	O(logn)	O(1)
867	Transpose Matrix	Java	N/A	N/A
875	Koko Eating Bananas	Java	N/A	N/A
977	Squares of a Sorted Array	Java	O(n)	O(n)		View discussion on leetcode
994	Rotting Oranges	Java	N/A	N/A
1004	Max Consecutive Ones III	Java	O(N + k)	O(1)
1207	Unique Number of Occurrences	Java	O(N)	O(N)
1268	Search Suggestions System	Java	N/A	N/A
1337	The K Weakest Rows in a Matrix	Java	O(nlogm)	O(n)		View discussion on leetcode
1346	Check If N and Its Double Exist	Java	N/A	N/A
1351	Count Negative Numbers in a Sorted Matrix	Java	N/A	N/A
1385	Find the Distance Value Between Two Arrays	Java	N/A	N/A
1431	Kids With the Greatest Number of Candies	Java	O(N)	O(N)
1480	Running Sum of 1D Array	Java	N/A	N/A
1491	Average Salary Excluding the Minimum and Maximum Salary	Java	N/A	N/A
1493	Longest Subarray of 1's After Deleting One Element	Java	O(N + k)	O(1)
1539	Kth Missing Positive Number	Java	O(logn)	O(n)
1572	Matrix Diagonal Sum	Java	O(n)	O(1)		View discussion on leetcode
1608	Special Array With X Elements Greater Than or Equal X	Java	O(nlogn)	O(1)		View discussion on leetcode
1672	Richest Customer Wealth	Java	N/A	N/A
1679	Max Number of K-Sum Pairs	Java	O(N)	O(1)
1732	Find the Highest Altitude	Java	O(N)	O(1)
1822	Sign of the Product of an Array	Java	N/A	N/A
1855	Maximum Distance Between a Pair of Values	Java	N/A	N/A
1863	Sum of All Subset XOR Totals	Java	N/A	N/A
1926	Nearest Exit from Entrance in Maze	Java	N/A	N/A
2215	Find the Difference of Two Arrays	Java	N/A	N/A
2300	Successful Pairs of Spells and Potions	Java	N/A	N/A
2352	Equal Row and Column Pairs	Java	O(N^3)	O(1)
2462	Total Cost to Hire K Workers	Java	N/A	N/A
2542	Maximum Subsequence Score	Java	N/A	N/A
2660	Determine the Winner of a Bowling Game	Java, Python, JavaScript	O(n)	O(1)		View discussion on leetcode

String

#	Title	Solution	Time	Space	Difficulty	Note
3	Longest Substring Without Repeating Characters	Java	N/A	N/A
5	Longest Palindromic Substring	Java	N/A	N/A
12	Integer to Roman	Java	N/A	N/A
13	Roman to Integer	Java	N/A	N/A
14	Longest Common Prefix	Java	N/A	N/A
17	Letter Combinations of a Phone Number	Java	N/A	N/A
20	Valid Parentheses	Java	N/A	N/A
22	Generate Parentheses	Java	N/A	N/A
28	Find the Index of the First Occurrence in a String	Java	N/A	N/A
32	Longest Valid Parentheses	Java	N/A	N/A
49	Group Anagrams	Java	N/A	N/A
58	Length of Last Word	Java	N/A	N/A
67	Add Binary	Java	N/A	N/A
72	Edit Distance	Java	N/A	N/A
76	Minimum Window Substring	Java	N/A	N/A
125	Valid Palindrome	Java	N/A	N/A
131	Palindrome Partitioning	Java	N/A	N/A
139	Word Break	Java	N/A	N/A
151	Reverse Words in a String	Java	O(N)	O(N)
168	Excel Sheet Column Title	Java	N/A	N/A
171	Excel Sheet Column Title	Java	O(n)	O(1)
205	Isomorphic Strings	Java	O(n)	O(1)
208	Implement Trie (Prefix Tree)	Java	N/A	N/A
242	Valid Anagram	Java	N/A	N/A
257	Binary Tree Paths	Java	N/A	N/A
290	Word Pattern	Java	N/A	N/A
344	Reverse String	Java	O(n)	O(1)
345	Reverse Vowels of a String	Java	O(N/2)	O(1)
383	Ransom Note	Java	N/A	N/A
387	First Unique Character in a String	Java	N/A	N/A
389	Find the Difference	Java	N/A	N/A
392	Is Subsequence	Java	N/A	N/A
394	Decode String	Java	N/A	N/A
412	Fizz Buzz	Java	N/A	N/A
438	Find All Anagrams in a String	Java	N/A	N/A
443	String Compression	Java	O(N^2)	O(1)
557	Reverse Words in a String III	Java	N/A	N/A
567	Permutation in String	Java	N/A	N/A
649	Dota2 Senate	Java	N/A	N/A
680	Valid Palindrome II	Java	N/A	N/A
763	Partition Labels	Java	N/A	N/A
784	Letter Case Permutation	Java	O(2^n)	O(2^n)		View discussion on leetcode
1143	Longest Common Subsequence	Java	N/A	N/A
1268	Search Suggestions System	Java	N/A	N/A
1456	Maximum Number of Vowels in a Substring of Given Length	Java	O(N)	O(1)
1657	Determine if Two Strings Are Close	Java	O(N)	O(1)
1768	Merge Strings Alternately	Java	O(N+M)	O(1)
2390	Removing Stars From a String	Java	O(N)	O(NlogN)

Linked List

#	Title	Solution	Time	Space	Difficulty	Note
2	Add Two Numbers	Java	N/A	N/A
19	Remove Nth Node From End of List	Java	N/A	N/A
21	Merge Two Sorted Lists	Java	N/A	N/A
23	Merge k Sorted Lists	Java	N/A	N/A
24	Swap Nodes in Pairs	Java	N/A	N/A
25	Reverse Nodes in k-Group	Java	N/A	N/A
83	Remove Duplicates from Sorted List	Java	N/A	N/A
114	Flatten Binary Tree to Linked List	Java	N/A	N/A
116	Populating Next Right Pointers in Each Node	Java	N/A	N/A
138	Copy List with Random Pointer	Java	N/A	N/A
141	Linked List Cycle	Java	N/A	N/A
142	Linked List Cycle II	Java	N/A	N/A
146	LRU Cache	Java	N/A	N/A
148	Sort List	Java	N/A	N/A
160	Intersection of Two Linked Lists	Java	N/A	N/A
206	Reverse Linked List	Java	O(n)	O(1)
234	Palindrome Linked List	Java	N/A	N/A
328	Odd Even Linked List	Java	O(N)	O(N)
876	Middle of the Linked List	Java	N/A	N/A
2095	Delete the Middle Node of a Linked List	Java	O(N)	O(N)
2130	Leaf Similar Trees	Java	O(N)	O(N)

Doubly Linked List

#	Title	Solution	Time	Space	Difficulty	Note
146	LRU Cache	Java	N/A	N/A

Two Pointers

#	Title	Solution	Time	Space	Difficulty	Note
11	Container With Most Water	Java	N/A	N/A
15	3Sum	Java	N/A	N/A
16	3Sum Closest	Java	N/A	N/A
18	4Sum	Java	N/A	N/A
19	Remove Nth Node From End of List	Java	N/A	N/A
26	Remove Duplicates from Sorted Array	Java	N/A	N/A
27	Remove Element	Java	N/A	N/A
28	Find the Index of the First Occurrence in a String	Java	N/A	N/A
31	Next Permutation	Java	N/A	N/A
42	Trapping Rain Water	Java	N/A	N/A
75	Sort Colors	Java	N/A	N/A
125	Valid Palindrome	Java	N/A	N/A
141	Linked List Cycle	Java	N/A	N/A
142	Linked List Cycle II	Java	N/A	N/A
148	Sort List	Java	N/A	N/A
151	Reverse Words in a String	Java	O(N)	O(N)
160	Intersection of Two Linked Lists	Java	N/A	N/A
167	Two Sum II - Input Array Is Sorted	Java	O(n)	O(1)		View discussion on leetcode
189	Rotate Array	Java	N/A	O(1)		View discussion on leetcode
202	Happy Number	Java	O(k∗logn)	O(k)		View discussion on leetcode
203	Remove Linked List Elements	Java	N/A	N/A
234	Palindrome Linked List	Java	N/A	N/A
283	Move Zeroes	Java	O(n)	O(1)		View discussion on leetcode
287	Find the Duplicate Number	Java	N/A	N/A
295	Find Median from Data Stream	Java	N/A	N/A
344	Reverse String	Java	O(n)	O(1)
345	Reverse Vowels of a String	Java	O(N/2)	O(1)
350	Intersection of Two Arrays II	Java	N/A	N/A
392	Is Subsequence	Java	N/A	N/A
443	String Compression	Java	O(N^2)	O(1)
455	Assign Cookies	Java	N/A	N/A
557	Reverse Words in a String III	Java	N/A	N/A
567	Permutation in String	Java	N/A	N/A
633	Sum of Square Numbers	Java	O(n)	O(1)
653	Two Sum IV - Input is a BST	Java	N/A	N/A
680	Valid Palindrome II	Java	N/A	N/A
763	Partition Labels	Java	N/A	N/A
876	Middle of the Linked List	Java	N/A	N/A
977	Squares of a Sorted Array	Java	O(n)	O(n)		View discussion on leetcode
1346	Check If N and Its Double Exist	Java	N/A	N/A
1385	Find the Distance Value Between Two Arrays	Java	N/A	N/A
1679	Max Number of K-Sum Pairs	Java	O(N)	O(1)
1768	Merge Strings Alternately	Java	O(N+M)	O(1)
1855	Maximum Distance Between a Pair of Values	Java	N/A	N/A
2095	Delete the Middle Node of a Linked List	Java	O(N)	O(N)
2130	Leaf Similar Trees	Java	O(N)	O(N)
2300	Successful Pairs of Spells and Potions	Java	N/A	N/A
2462	Total Cost to Hire K Workers	Java	N/A	N/A

Combinatorics

#	Title	Solution	Time	Space	Difficulty	Note
62	Unique Paths	Java	N/A	N/A		View discussion on leetcode
1863	Sum of All Subset XOR Totals	Java	N/A	N/A

Counting

#	Title	Solution	Time	Space	Difficulty	Note
169	Majority Element	Java	N/A	N/A
347	Top K Frequent Elements	Java	N/A	N/A
383	Ransom Note	Java	N/A	N/A
387	First Unique Character in a String	Java	N/A	N/A

Union Find

#	Title	Solution	Time	Space	Difficulty	Note
128	Longest Consecutive Sequence	Java	N/A	N/A
200	Number of Islands	Java	N/A	N/A
399	Evaluate Division	Java	N/A	N/A
547	Number of Provinces	Java	N/A	N/A
695	Max Area of Island	Java	N/A	N/A

Topological Sort

#	Title	Solution	Time	Space	Difficulty	Note
207	Course Schedule	Java	N/A	N/A

Bucket Sort

#	Title	Solution	Time	Space	Difficulty	Note
347	Top K Frequent Elements	Java	N/A	N/A

Merge Sort

#	Title	Solution	Time	Space	Difficulty	Note
23	Merge k Sorted Lists	Java	N/A	N/A
148	Sort List	Java	N/A	N/A

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⚡ JavaScript

JS

#	Title	Solution	Time	Space	Difficulty	Note
2618	Check if Object Instance of Class	JavaScript	N/A	N/A
2619	Array Prototype Last	JavaScript	N/A	N/A
2620	Counter	JavaScript	N/A	N/A
2621	Sleep	JavaScript	N/A	N/A
2634	Filter Elements from Array	JavaScript	N/A	N/A
2648	Generate Fibonacci Sequence	JavaScript	N/A	N/A
2665	Counter II	JavaScript	N/A	N/A
2666	Allow One Function Call	JavaScript	N/A	N/A
2667	Create Hello World Function	JavaScript	N/A	N/A
2703	Return Length of Arguments Passed	JavaScript	N/A	N/A
2704	To Be Or Not To Be	JavaScript	N/A	N/A
2724	Sort By	JavaScript	N/A	N/A
2726	Calculator with Method Chaining	JavaScript	N/A	N/A
2727	Is Object Empty	JavaScript	N/A	N/A

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🛄 Database

SQL

#	Title	Solution	Time	Space	Difficulty	Note
-----	----------------	---------------	---------------	---------------	-------------	--------------

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🔑 Shell

Shell Script

#	Title	Solution	Time	Space	Difficulty	Note
-----	----------------	---------------	---------------	---------------	-------------	--------------

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🔥 Concurrency

Concurrency

#	Title	Solution	Time	Space	Difficulty	Note
-----	----------------	---------------	---------------	---------------	-------------	--------------

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📜 Useful Information

References

• ▶ Data Structures and Algorithms on YouTube
• ✍🏻 Data Structure Sketches
• 💻 Personal LeetCode Account
• See REFERENCE.md for more information.

Big O Notation

Big O notation is used to classify algorithms according to how their running time or space requirements grow as the input size grows. On the chart below you may find most common orders of growth of algorithms specified in Big O notation.

Source: Big O Cheat Sheet.

Below is the list of some of the most used Big O notations and their performance comparisons against different sizes of the input data.

Big O Notation	Type	Computations for 10 elements	Computations for 100 elements	Computations for 1000 elements
O(1)	Constant	1	1	1
O(log N)	Logarithmic	3	6	9
O(N)	Linear	10	100	1000
O(N log N)	n log(n)	30	600	9000
O(N^2)	Quadratic	100	10000	1000000
O(2^N)	Exponential	1024	1.26e+29	1.07e+301
O(N!)	Factorial	3628800	9.3e+157	4.02e+2567

Data Structure Operations Complexity

Data Structure	Access	Search	Insertion	Deletion	Comments
Array	1	n	n	n
Stack	n	n	1	1
Queue	n	n	1	1
Linked List	n	n	1	n
Hash Table	-	n	n	n	In case of perfect hash function costs would be O(1)
Binary Search Tree	n	n	n	n	In case of balanced tree costs would be O(log(n))
B-Tree	log(n)	log(n)	log(n)	log(n)
Red-Black Tree	log(n)	log(n)	log(n)	log(n)
AVL Tree	log(n)	log(n)	log(n)	log(n)
Bloom Filter	-	1	1	-	False positives are possible while searching

Array Sorting Algorithms Complexity

Name	Best	Average	Worst	Memory	Stable	Comments
Bubble sort	n	n2	n2	1	Yes
Insertion sort	n	n2	n2	1	Yes
Selection sort	n2	n2	n2	1	No
Heap sort	n log(n)	n log(n)	n log(n)	1	No
Merge sort	n log(n)	n log(n)	n log(n)	n	Yes
Quick sort	n log(n)	n log(n)	n2	log(n)	No	Quicksort is usually done in-place with O(log(n)) stack space
Shell sort	n log(n)	depends on gap sequence	n (log(n))2	1	No
Counting sort	n + r	n + r	n + r	n + r	Yes	r - biggest number in array
Radix sort	n * k	n * k	n * k	n + k	Yes	k - length of longest key

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👋 Contributing

Contributions are always welcome!

See contributing.md for ways to get started.

Contributions are what make the open source community such an amazing place to learn, inspire, and create. Any contributions you make are greatly appreciated.

If you have a suggestion that would make this better, please fork the repo and create a pull request. You can also simply open an issue with the tag "enhancement". Don't forget to give the project a star! Thanks again!

1. Fork the Project
2. Create your Feature Branch (git checkout -b feature/AmazingFeature)
3. Commit your Changes (git commit -m 'Add some AmazingFeature')
4. Push to the Branch (git push origin feature/AmazingFeature)
5. Open a Pull Request

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⚠️ License

Distributed under the MIT License. See LICENSE.txt for more information.

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🤝 Author

@lironabutbul

A few more projects and study materials about Computer-Science on ladunjexa.

Get in touch - on LinkedIn - on Telegram

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