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LanguageΒ  LicenseΒ  SayThanksΒ  Visitors

  • R.I.P. to my old Leetcode repository, where there were 5.7k+ stars and 2.2k+ forks (ever the top 3 in the field).
  • Since free questions may be even mistakenly taken down by some companies, only solutions will be post on now.
  • There are new LeetCode questions every week. I'll keep updating for full summary and better solutions.
  • For more problem solutions, you can see my LintCode, GoogleKickStart repositories.
  • For more challenging problem solutions, you can also see my GoogleCodeJam, FacebookHackerCup repositories.
  • Hope you enjoy the journey of learning data structures and algorithms.
  • Notes: "πŸ”’" means your subscription of LeetCode premium membership is required for reading the question.

Solutions

Algorithms

Database

Shell

Reference

n Complexity Possible Algorithms & Techniques
1018+ O(1) Math
1018 O(logn) Binary & Ternary Search / Matrix Power / Cycle Tricks / Big Simulation Steps / Values Reranking / Math
1016 O(n1/2) Math
108 O(n) Greedy / Ad-hoc / DP
4Γ—107 O(nlogn) Linear # Calls to Binary & Ternary Search / Pre-processing & Querying / Divide and Conquer
104 O(n2) Ad-hoc / DP / Greedy / Divide and Conquer / Branch and Bound
500 O(n3) Ad-hoc / DP / Greedy / Divide and Conquer / Branch and Bound
90 O(n4) Ad-hoc / DP / Greedy / Divide and Conquer / Branch and Bound
50 O(n5) Branch and Bound
40 O(nx2n/2) Meet in the Middle
20 O(nΓ—2n) Backtracking / Generating 2n Subsets / Bitmask Technique
11 O(n!) Factorial / Permutation / Combination Algorithm

Bit Manipulation

# Title Solution Time Space Difficulty Tag Note
0136 Single Number C++ Python O(n) O(1) Easy
0137 Single Number II C++ Python O(n) O(1) Medium
0190 Reverse Bits C++ Python O(1) O(1) Easy
0191 Number of 1 Bits C++ Python O(1) O(1) Easy
0201 Bitwise AND of Numbers Range C++ Python O(1) O(1) Medium
0231 Power of Two C++ Python O(1) O(1) Easy LintCode
0260 Single Number III C++ Python O(n) O(1) Medium
0268 Missing Number C++ Python O(n) O(1) Medium LintCode
0318 Maximum Product of Word Lengths C++ Python O(n) ~ O(n^2) O(n) Medium Bit Manipulation, Counting Sort, Pruning
0342 Power of Four C++ Python O(1) O(1) Easy
0371 Sum of Two Integers C++ Python O(1) O(1) Easy LintCode
0389 Find the Difference C++ Python O(n) O(1) Easy
0393 UTF-8 Validation C++ Python O(n) O(1) Medium
0401 Binary Watch C++ Python O(1) O(1) Easy
0411 Minimum Unique Word Abbreviation C++ Python O((d + n) * 2^n) O(d) Hard πŸ”’
0421 Maximum XOR of Two Numbers in an Array C++ Python O(nlogk) O(n) Medium Greedy, Trie
0461 Hamming Distance C++ Python O(1) O(1) Easy
0476 Number Complement C++ Python O(1) O(1) Easy Bit Manipulation
0477 Total Hamming Distance C++ Python O(n) O(1) Medium
0645 Set Mismatch C++ Python O(n) O(1) Easy
0693 Binary Number with Alternating Bits C++ Python O(1) O(1) Easy
0762 Prime Number of Set Bits in Binary Representation C++ Python O(1) O(1) Easy
0868 Binary Gap C++ Python O(1) O(1) Easy
0898 Bitwise ORs of Subarrays C++ Python O(n) O(1) Medium


Array

# Title Solution Time Space Difficulty Tag Note
0026 Remove Duplicates from Sorted Array C++ Python O(n) O(1) Easy Two Pointers
0027 Remove Element C++ Python O(n) O(1) Easy
0031 Next Permutation C++ Python O(n) O(1) Medium Tricky
0041 First Missing Positive C++ Python O(n) O(1) Hard Tricky
0048 Rotate Image C++ Python O(n^2) O(1) Medium Inplace
0054 Spiral Matrix C++ Python O(m * n) O(1) Medium
0059 Spiral Matrix II C++ Python O(n^2) O(1) Medium
0066 Plus One C++ Python O(n) O(1) Easy
0073 Set Matrix Zeroes C++ Python O(m * n) O(1) Medium
0080 Remove Duplicates from Sorted Array II C++ Python O(n) O(1) Medium Two Pointers
0118 Pascal's Triangle C++ Python O(n^2) O(1) Easy
0119 Pascal's Triangle II C++ Python O(n^2) O(1) Easy
0121 Best Time to Buy and Sell Stock C++ Python O(n) O(1) Easy
0128 Longest Consecutive Sequence C++ Python O(n) O(n) Hard Tricky
0157 Read N Characters Given Read4 C++ Python O(n) O(1) Easy πŸ”’
0158 Read N Characters Given Read4 II - Call multiple times C++ Python O(n) O(1) Hard πŸ”’
0163 Missing Ranges C++ Python O(n) O(1) Medium πŸ”’
0169 Majority Element C++ Python O(n) O(1) Easy Boyer–Moore Majority Vote Algorithm
0189 Rotate Array C++ Python O(n) O(1) Easy Inplace
0215 Kth Largest Element in an Array C++ Python O(n) on average O(1) Medium EPI Quick Select, Tri Partition
0228 Summary Ranges C++ Python O(n) O(1) Medium
0229 Majority Element II C++ Python O(n) O(1) Medium
0238 Product of Array Except Self C++ Python O(n) O(1) Medium LintCode
0240 Search a 2D Matrix II C++ Python O(m + n) O(1) Medium EPI, LintCode
0243 Shortest Word Distance C++ Python O(n) O(1) Easy πŸ”’
0245 Shortest Word Distance III C++ Python O(n) O(1) Medium πŸ”’
0251 Flatten 2D Vector C++ Python O(1) O(1) Medium πŸ”’
0277 Find the Celebrity C++ Python O(n) O(1) Medium πŸ”’, EPI
0289 Game of Life C++ Python O(m * n) O(1) Medium
0293 Flip Game C++ Python O(n * (c+1)) O(1) Easy πŸ”’
0296 Best Meeting Point C++ Python O(m * n) O(m + n) Hard πŸ”’
0311 Sparse Matrix Multiplication C++ Python O(m * n * l) O(m * l) Medium πŸ”’
0334 Increasing Triplet Subsequence C++ Python O(n) O(1) Medium
0370 Range Addition C++ Python O(k + n) O(1) Medium πŸ”’
0384 Shuffle an Array C++ Python O(n) O(n) Medium EPI
0396 Rotate Function C++ Python O(n) O(1) Easy
0412 Fizz Buzz C++ Python O(n) O(1) Easy
0414 Third Maximum Number C++ Python O(n) O(1) Easy
0419 Battleships in a Board C++ Python O(m * n) O(1) Medium
0422 Valid Word Square C++ Python O(m * n) O(1) Easy πŸ”’
0442 Find All Duplicates in an Array C++ Python O(n) O(1) Medium
0448 Find All Numbers Disappeared in an Array C++ Python O(n) O(1) Easy
0462 Minimum Moves to Equal Array Elements II C++ Python O(n) on average O(1) Medium Math, Median, Quick Select
0463 Island Perimeter C++ Python O(m * n) O(1) Easy Array
0485 Max Consecutive Ones C++ Python O(n) O(1) Easy Array
0487 Max Consecutive Ones II C++ Python O(n) O(1) Medium πŸ”’ Array
0495 Teemo Attacking C++ Python O(n) O(1) Easy Array, Simulation
0498 Diagonal Traverse C++ Python O(m * n) O(1) Medium Array
0506 Relative Ranks C++ Python O(nlogn) O(n) Easy Array, Sort
0531 Lonely Pixel I C++ Python O(m * n) O(m + n) Medium πŸ”’
0533 Lonely Pixel II C++ Python O(m * n) O(m * n) Medium πŸ”’
0565 Array Nesting C++ Python O(n) O(1) Medium
0566 Reshape the Matrix C++ Python O(m * n) O(m * n) Easy
0581 Shortest Unsorted Continuous Subarray C++ Python O(n) O(1) Easy
0605 Can Place Flowers C++ Python O(n) O(1) Easy
0624 Maximum Distance in Arrays C++ Python O(n) O(1) Easy πŸ”’
0643 Maximum Average Subarray I C++ Python O(n) O(1) Easy Math
0644 Maximum Average Subarray II C++ Python O(n) O(n) Hard πŸ”’ Math
0661 Image Smoother C++ Python O(m * n) O(1) Easy
0665 Non-decreasing Array C++ Python O(n) O(1) Easy
0667 Beautiful Arrangement II C++ Python O(n) O(1) Medium
0670 Maximum Swap C++ Python O(logn) O(logn) Medium
0674 Longest Continuous Increasing Subsequence C++ Python O(n) O(1) Easy
0683 K Empty Slots C++ Python O(n) O(n) Hard
0697 Degree of an Array C++ Python O(n) O(n) Easy
0713 Subarray Product Less Than K C++ Python O(n) O(1) Medium
0717 1-bit and 2-bit Characters C++ Python O(n) O(1) Easy Greedy
0723 Candy Crush C++ Python O((R * C)^2) O(1) Medium
0724 Find Pivot Index C++ Python O(n) O(1) Easy
0729 My Calendar I C++ Python O(nlogn) O(n) Medium
0731 My Calendar II C++ Python O(n^2) O(n) Medium
0732 My Calendar III C++ Python O(nlogn) ~ O(n^2) O(n) Hard
0747 Largest Number At Least Twice of Others C++ Python O(n) O(1) Easy
0755 Pour Water C++ Python O(v * n) O(1) Medium
0766 Toeplitz Matrix C++ Python O(m * n) O(1) Easy
0768 Max Chunks To Make Sorted II C++ Python O(n) O(n) Hard Mono Stack
0769 Max Chunks To Make Sorted C++ Python O(n) O(1) Medium
0778 Swim in Rising Water C++ Python O(n^2) O(n^2) Hard Union Find
0792 Number of Matching Subsequences C++ Python O(n + w) O(k) Medium
0794 Valid Tic-Tac-Toe State C++ Python O(1) O(1) Medium
0795 Number of Subarrays with Bounded Maximum C++ Python O(n) O(1) Medium
0803 Bricks Falling When Hit C++ Python O(r * c) O(r * c) Hard Union Find
0807 Max Increase to Keep City Skyline C++ Python O(n^2) O(n) Medium
0821 Shortest Distance to a Character C++ Python O(n) O(1) Easy
0830 Positions of Large Groups C++ Python O(n) O(1) Easy
0832 Flipping an Image C++ Python O(n^2) O(1) Easy
0835 Image Overlap C++ Python O(n^4) O(n^2) Medium
0840 Magic Squares In Grid C++ Python O(m * n) O(1) Easy
0842 Split Array into Fibonacci Sequence C++ Python O(n^3) O(n) Medium
0845 Longest Mountain in Array C++ Python O(n) O(1) Medium
0849 Maximize Distance to Closest Person C++ Python O(n) O(1) Easy
0860 Lemonade Change C++ Python O(n) O(1) Easy
0867 Transpose Matrix C++ Python O(r * c) O(1) Easy
0885 Spiral Matrix III C++ Python O(max(m, n)^2) O(1) Medium
0888 Fair Candy Swap C++ Python O(m + n) O(m + n) Easy
0896 Monotonic Array C++ Python O(n) O(1) Easy
0905 Sort Array By Parity C++ Python O(n) O(1) Easy
0909 Snakes and Ladders C++ Python O(n^2) O(n^2) Medium
0915 Partition Array into Disjoint Intervals C++ Python O(n) O(n) Medium
0918 Maximum Sum Circular Subarray C++ Python O(n) O(1) Medium
0922 Sort Array By Parity II C++ Python O(n) O(1) Easy
0923 3Sum With Multiplicity C++ Python O(n^2) O(n) Medium
0927 Three Equal Parts C++ Python O(n) O(1) Hard
0932 Beautiful Array C++ Python O(n) O(n) Medium
0941 Valid Mountain Array C++ Python O(n) O(1) Easy
0945 Minimum Increment to Make Array Unique C++ Python O(nlogn) O(n) Medium
0947 Most Stones Removed with Same Row or Column C++ Python O(n) O(n) Medium Union Find
0949 Largest Time for Given Digits C++ Python O(1) O(1) Easy
0950 Reveal Cards In Increasing Order C++ Python O(n) O(n) Medium
0952 Largest Component Size by Common Factor C++ Python O(f * n) O(p + n) Hard Union Find
0954 Array of Doubled Pairs C++ Python O(n + klogk) O(k) Medium
0961 N-Repeated Element in Size 2N Array C++ Python O(n) O(1) Easy
0978 Longest Turbulent Subarray C++ Python O(n) O(1) Medium
0985 Sum of Even Numbers After Queries C++ Python O(n + q) O(1) Easy
0989 Add to Array-Form of Integer C++ Python O(n + logk) O(1) Easy
0997 Find the Town Judge C++ Python O(t + n) O(n) Easy
0999 Available Captures for Rook C++ Python O(1) O(1) Easy


String

# Title Solution Time Space Difficulty Tag Note
0005 Longest Palindromic Substring C++ Python O(n) O(n) Medium Manacher's Algorithm
0006 ZigZag Conversion C++ Python O(n) O(1) Easy
0008 String to Integer (atoi) C++ Python O(n) O(1) Easy
0014 Longest Common Prefix C++ Python O(n * k) O(1) Easy
0028 Implement strStr() C++ Python O(n + k) O(k) Easy KMP Algorithm
0038 Count and Say C++ Python O(n * 2^n) O(2^n) Easy
0043 Multiply Strings C++ Python O(m * n) O(m + n) Medium
0058 Length of Last Word C++ Python O(n) O(1) Easy
0067 Add Binary C++ Python O(n) O(1) Easy
0068 Text Justification C++ Python O(n) O(1) Hard
0125 Valid Palindrome C++ Python O(n) O(1) Easy
0151 Reverse Words in a String C++ Python O(n) O(1) Medium
0161 One Edit Distance C++ Python O(m + n) O(1) Medium πŸ”’
0165 Compare Version Numbers C++ Python O(n) O(1) Easy
0186 Reverse Words in a String II C++ Python O(n) O(1) Medium πŸ”’
0214 Shortest Palindrome C++ Python O(n) O(n) Hard KMP Algorithm, Manacher's Algorithm
0242 Valid Anagram C++ Python O(n) O(1) Easy LintCode
0271 Encode and Decode Strings C++ Python O(n) O(1) Medium πŸ”’
0273 Integer to English Words C++ Python O(1) O(1) Hard
0306 Addictive Number C++ Python O(n^3) O(n) Medium
0383 Ransom Note C++ Python O(n) O(1) Easy EPI
0405 Convert a Number to Hexadecimal C++ Python O(n) O(1) Easy
0408 Valid Word Abbreviation C++ Python O(n) O(1) Easy πŸ”’
0415 Add Strings C++ Python O(n) O(1) Easy
0420 Strong Password Checker C++ Python O(n) O(1) Hard
0434 Number of Segments in a String C++ Python O(n) O(1) Easy
0443 String Compression C++ Python O(n) O(1) Easy
0459 Repeated Substring Pattern C++ Python O(n) O(n) Easy KMP Algorithm
0468 Validate IP Address C++ Python O(1) O(1) Medium
0481 Magical String C++ Python O(n) O(n) Medium String
0482 License Key Formatting C++ Python O(n) O(1) Easy
0500 Keyboard Row C++ Python O(n) O(1) Easy String, Hash
0520 Detect Capital C++ Python O(l) O(1) Easy
0521 Longest Uncommon Subsequence I C++ Python O(min(a, b)) O(1) Easy
0522 Longest Uncommon Subsequence II C++ Python O(l * n^2) O(1) Medium Sort
0524 Longest Word in Dictionary through Deleting C++ Python O((d * l) * logd) O(1) Medium Sort
0527 Word Abbreviation C++ Python O(n * l) ~ O(n^2 * l^2) O(n * l) Hard πŸ”’
0539 Minimum Time Difference C++ Python O(nlogn) O(n) Medium
0541 Reverse String II C++ Python O(n) O(1) Easy
0551 Student Attendance Record I C++ Python O(n) O(1) Easy
0555 Split Concatenated Strings C++ Python O(n^2) O(n) Medium String
0556 Next Greater Element III C++ Python O(1) O(1) Medium
0557 Reverse Words in a String III C++ Python O(n) O(1) Easy
0564 Find the Closest Palindrome C++ Python O(l) O(l) Hard
0591 Tag Validator C++ Python O(n) O(n) Hard
0616 Add Bold Tag in String C++ Python O(n * d * l) O(n) Medium πŸ”’
0647 Palindromic Substrings C++ Python O(n) O(n) Medium Manacher's Algorithm
0648 Replace Words C++ Python O(n) O(t) Medium Trie
0657 Robot Return to Origin C++ Python O(n) O(1) Easy
0678 Valid Parenthesis String C++ Python O(n) O(1) Medium
0680 Valid Palindrome II C++ Python O(n) O(1) Easy
0681 Next Closest Time C++ Python O(1) O(1) Medium
0686 Repeated String Match C++ Python O(n + m) O(1) Easy Rabin-Karp Algorithm
0696 Count Binary Substrings C++ Python O(n) O(1) Easy
0709 To Lower Case C++ Python O(n) O(1) Easy String
0720 Longest Word in Dictionary C++ Python O(n) O(t) Easy Trie
0722 Remove Comments C++ Python O(n) O(k) Medium
0751 IP to CIDR C++ Python O(n) O(1) Medium
0758 Bold Words in String C++ Python O(n * l) O(t) Easy πŸ”’, variant of Add Bold Tag in String
0791 Custom Sort String C++ Python O(n) O(1) Medium
0796 Rotate String C++ Python O(n) O(1) Easy KMP Algorithm, Rabin-Karp Algorithm
0804 Unique Morse Code Words C++ Python O(n) O(n) Easy
0806 Number of Lines To Write String C++ Python O(n) O(1) Easy
0809 Expressive Words C++ Python O(n + s) O(l + s) Medium
0816 Ambiguous Coordinates C++ Python O(n^4) O(n) Medium
0819 Most Common Word C++ Python O(m + n) O(m + n) Easy
0820 Short Encoding of Words C++ Python O(n) O(t) Medium Trie
0824 Goat Latin C++ Python O(n + w^2) O(l) Easy
0831 Masking Personal Information C++ Python O(1) O(1) Medium
0833 Find And Replace in String C++ Python O(n + m) O(n) Medium
0839 Similar String Groups C++ Python O(n^2 * l) O(n) Hard Union Find
0848 Shifting Letters C++ Python O(n) O(1) Medium
0859 Buddy Strings C++ Python O(n) O(1) Easy
0880 Decoded String at Index C++ Python O(n) O(1) Medium
0884 Uncommon Words from Two Sentences C++ Python O(m + n) O(m + n) Easy
0890 Find and Replace Pattern C++ Python O(n * l) O(1) Medium
0893 Groups of Special-Equivalent Strings C++ Python O(n * l) O(n) Easy
0916 Word Subsets C++ Python O(m + n) O(1) Medium
0917 Reverse Only Letters C++ Python O(n) O(1) Easy
0925 Long Pressed Name C++ Python O(n) O(1) Easy
0929 Unique Email Addresses C++ Python O(n * l) O(n * l) Easy
0939 Minimum Area Rectangle C++ Python O(n^1.5) on average O(n) Medium
0942 DI String Match C++ Python O(n) O(1) Easy
0944 Delete Columns to Make Sorted C++ Python O(n * l) O(1) Medium
0953 Verifying an Alien Dictionary C++ Python O(n * l) O(1) Easy
0955 Delete Columns to Make Sorted II C++ Python O(n * l) O(n) Medium


Linked List

# Title Solution Time Space Difficulty Tag Note
0002 Add Two Numbers C++ Python O(n) O(1) Medium
0021 Merge Two Sorted Lists C++ Python O(n) O(1) Easy
0023 Merge k Sorted Lists C++ Python O(nlogk) O(1) Hard Heap, Divide and Conquer
0024 Swap Nodes in Pairs C++ Python O(n) O(1) Easy
0025 Reverse Nodes in k-Group C++ Python O(n) O(1) Hard
0061 Rotate List C++ Python O(n) O(1) Medium
0082 Remove Duplicates from Sorted List II C++ Python O(n) O(1) Medium
0083 Remove Duplicates from Sorted List C++ Python O(n) O(1) Easy
0092 Reverse Linked List II C++ Python O(n) O(1) Medium
0138 Copy List with Random Pointer C++ Python O(n) O(1) Medium
0160 Intersection of Two Linked Lists C++ Python O(m + n) O(1) Easy
0203 Remove Linked List Elements C++ Python O(n) O(1) Easy
0206 Reverse Linked List C++ Python O(n) O(1) Easy
0234 Palindrome Linked List C++ Python O(n) O(1) Easy
0237 Delete Node in a Linked List C++ Python O(1) O(1) Easy LintCode
0328 Odd Even Linked List C++ Python O(n) O(1) Medium
0369 Plus One Linked List C++ Python O(n) O(1) Medium πŸ”’ Two Pointers
0445 Add Two Numbers II C++ Python O(m + n) O(m + n) Medium
0708 Insert into a Sorted Circular Linked List C++ Python O(n) O(1) Medium πŸ”’ Linked List
0725 Split Linked List in Parts C++ Python O(n + k) O(1) Medium
0817 Linked List Components C++ Python O(m + n) O(m) Medium
0986 Interval List Intersections C++ Python O(m + n) O(1) Medium


Stack

# Title Solution Time Space Difficulty Tag Note
0020 Valid Parentheses C++ Python O(n) O(n) Easy
0032 Longest Valid Parentheses C++ Python O(n) O(1) Hard
0071 Simplify Path C++ Python O(n) O(n) Medium
0084 Largest Rectangle in Histogram C++ Python O(n) O(n) Hard Mono Stack, DP
0085 Maximal Rectangle C++ Python O(m * n) O(n) Hard EPI Mono Stack
0101 Symmetric Tree C++ Python O(n) O(h) Easy
0150 Evaluate Reverse Polish Notation C++ Python O(n) O(n) Medium
0155 Min Stack C++ Python O(n) O(1) Easy
0224 Basic Calculator C++ Python O(n) O(n) Hard
0227 Basic Calculator II C++ Python O(n) O(n) Medium
0232 Implement Queue using Stacks C++ Python O(1), amortized O(n) Easy EPI, LintCode
0255 Verify Preorder Sequence in Binary Search Tree C++ Python O(n) O(1) Medium πŸ”’
0272 Closest Binary Search Tree Value II C++ Python O(h + k) O(h) Hard πŸ”’
0331 Verify Preorder Serialization of a Binary Tree C++ Python O(n) O(1) Medium
0341 Flatten Nested List Iterator C++ Python O(n) O(h) Medium πŸ”’ Iterator
0385 Mini Parser C++ Python O(n) O(h) Medium
0394 Decode String C++ Python O(n) O(n) Medium
0439 Ternary Expression Parser C++ Python O(n) O(1) Medium πŸ”’
0456 132 Pattern C++ Python O(n) O(n) Medium
0496 Next Greater Element I C++ Python O(m + n) O(m + n) Easy Mono Stack
0503 Next Greater Element II C++ Python O(n) O(n) Medium Mono Stack
0636 Exclusive Time of Functions C++ Python O(n) O(n) Medium
0682 Baseball Game C++ Python O(n) O(n) Easy
0726 Number of Atoms C++ Python O(n) O(n) Hard
0735 Asteroid Collision C++ Python O(n) O(n) Medium
0736 Parse Lisp Expression C++ Python O(n^2) O(n^2) Hard
0739 Daily Temperatures C++ Python O(n) O(n) Medium
0770 Basic Calculator IV C++ Python add: O(d * t)
sub: O(d * t)
mul: O(d * t^2)
eval: O(d * t)
to_list: O(d * tlogt)
O(e + d * t) Hard
0772 Basic Calculator III C++ Python O(n) O(n) Hard
0853 Car Fleet C++ Python O(nlogn) O(n) Medium
0856 Score of Parentheses C++ Python O(n) O(1) Medium
0872 Leaf-Similar Trees C++ Python O(n) O(h) Easy
0895 Maximum Frequency Stack C++ Python O(1) O(n) Hard Hash
0901 Online Stock Span C++ Python O(n) O(n) Medium
0921 Minimum Add to Make Parentheses Valid C++ Python O(n) O(1) Medium
0946 Validate Stack Sequences C++ Python O(n) O(n) Medium


Queue

# Title Solution Time Space Difficulty Tag Note
0239 Sliding Window Maximum C++ Python O(n) O(k) Hard EPI, LintCode Mono Deque
0281 Zigzag Iterator C++ Python O(n) O(k) Medium πŸ”’
0346 Moving Average from Data Stream C++ Python O(1) O(w) Easy πŸ”’
0933 Number of Recent Calls C++ Python O(1) on average O(w) Easy


Binary Heap

# Title Solution Time Space Difficulty Tag Note
0264 Ugly Number II C++ Python O(n) O(1) Medium CTCI, LintCode BST, Heap
0295 Find Median from Data Stream C++ Python O(nlogn) O(n) Hard EPI, LintCode BST, Heap
0313 Super Ugly Number C++ Python O(n * k) O(n + k) Medium BST, Heap
0358 Rearrange String k Distance Apart C++ Python O(n) O(n) Hard πŸ”’ Greedy, Heap
0373 Find K Pairs with Smallest Sums C++ Python O(k * log(min(n, m, k))) O(min(n, m, k)) Medium
0378 Kth Smallest Element in a Sorted Matrix C++ Python O(k * log(min(n, m, k))) O(min(n, m, k)) Medium LintCode
0407 Trapping Rain Water II C++ Python O(m * n * (logm + logn)) O(m * n) Hard LintCode
0480 Sliding Window Median C++ Python O(nlogk) O(k) Hard BST, Heap
0502 IPO C++ Python O(nlogn) O(n) Hard Heap
0632 Smallest Range C++ Python O(nlogk) O(k) Hard
0703 Kth Largest Element in a Stream C++ Python O(nlogk) O(k) Easy
0846 Hand of Straights C++ Python O(nlogn) O(n) Medium
0855 Exam Room C++ Python seat: O(logn)
leave: O(logn)
O(n) Medium BST, Hash
0857 Minimum Cost to Hire K Workers C++ Python O(nlogn) O(n) Hard Sort
0871 Minimum Number of Refueling Stops C++ Python O(nlogn) O(n) Hard Sort


Tree

# Title Solution Time Space Difficulty Tag Note
0094 Binary Tree Inorder Traversal C++ Python O(n) O(1) Medium Morris Traversal
0099 Recover Binary Search Tree C++ Python O(n) O(1) Hard Morris Traversal
0144 Binary Tree Preorder Traversal C++ Python O(n) O(1) Medium Morris Traversal
0145 Binary Tree Postorder Traversal C++ Python O(n) O(1) Hard Morris Traversal
0208 Implement Trie (Prefix Tree) C++ Python O(n) O(1) Medium Trie
0211 Add and Search Word - Data structure design C++ Python O(min(n, h)) O(min(n, h)) Medium Trie, DFS
0226 Invert Binary Tree C++ Python O(n) O(h), O(w) Easy
0297 Serialize and Deserialize Binary Tree C++ Python O(n) O(h) Hard LintCode DFS
0307 Range Sum Query - Mutable C++ Python ctor: O(n), update: O(logn), query: O(logn) O(n) Medium LintCode DFS, Segment Tree, BIT, Fenwick Tree
0308 Range Sum Query 2D - Mutable C++ Python ctor: O(m * n), update: O(logm * logn), query: O(logm * logn) O(m * n) Hard πŸ”’ DFS, Quad Tree, 2D BIT, 2D Fenwick Tree
0315 Count of Smaller Numbers After Self C++ Python O(nlogn) O(n) Hard LintCode BST, BIT, Fenwick Tree, Divide and Conquer, Merge Sort
0426 Convert Binary Search Tree to Sorted Doubly Linked List C++ Python O(n) O(h) Medium πŸ”’
0427 Construct Quad Tree C++ Python O(n) O(h) Medium
0428 Serialize and Deserialize N-ary Tree C++ Python O(n) O(h) Hard πŸ”’
0429 N-ary Tree Level Order Traversal C++ Python O(n) O(w) Medium
0430 Flatten a Multilevel Doubly Linked List C++ Python O(n) O(1) Medium
0431 Encode N-ary Tree to Binary Tree C++ Python O(n) O(h) Hard πŸ”’
0501 Find Mode in Binary Search Tree C++ Python O(n) O(1) Easy Tree, Inorder Traversal
0508 Most Frequent Subtree Sum C++ Python O(n) O(n) Medium Tree, DFS, Hash
0513 Find Bottom Left Tree Value C++ Python O(n) O(h) Medium Tree, DFS, BFS
0525 Contiguous Array C++ Python O(n) O(n) Medium
0529 Minesweeper C++ Python O(m * n) O(m + n) Medium
0536 Construct Binary Tree from String C++ Python O(n) O(h) Medium πŸ”’
0538 Convert BST to Greater Tree C++ Python O(n) O(h) Easy
0543 Diameter of Binary Tree C++ Python O(n) O(h) Easy
0545 Boundary of Binary Tree C++ Python O(n) O(h) Medium πŸ”’
0548 Split Array with Equal Sum C++ Python O(n^2) O(n) Medium πŸ”’
0558 Logical OR of Two Binary Grids Represented as Quad-Trees C++ Python O(n) O(h) Medium Tree, Divide and Conquer
0559 Max Consecutive Ones C++ Python O(n) O(h) Easy Tree, DFS
0563 Binary Tree Tilt C++ Python O(n) O(n) Easy
0572 Subtree of Another Tree C++ Python O(m * n) O(h) Easy
0589 N-ary Tree Preorder Traversal C++ Python O(n) O(h) Easy Tree, Preorder Traversal
0590 N-ary Tree Postorder Traversal C++ Python O(n) O(h) Medium Tree, Preorder Traversal
0606 Construct String from Binary Tree C++ Python O(n) O(h) Easy
0617 Merge Two Binary Trees C++ Python O(n) O(h) Easy
0623 Add One Row to Tree C++ Python O(n) O(h) Medium
0637 Average of Levels in Binary Tree C++ Python O(n) O(h) Easy
0652 Find Duplicate Subtrees C++ Python O(n) O(n) Medium DFS, Hash
0653 Two Sum IV - Input is a BST C++ Python O(n) O(h) Easy Two Pointers
0654 Maximum Binary Tree C++ Python O(n) O(n) Medium LintCode Mono Stack, Cartesian Tree
0655 Print Binary Tree C++ Python O(n) O(h) Medium
0662 Maximum Width of Binary Tree C++ Python O(n) O(h) Medium DFS
0663 Equal Tree Partition C++ Python O(n) O(n) Medium πŸ”’ Hash
0677 Map Sum Pairs C++ Python O(n) O(t) Medium Trie
0684 Redundant Connection C++ Python O(n) O(n) Medium Union Find
0685 Redundant Connection II C++ Python O(n) O(n) Hard Union Find
0687 Longest Univalue Path C++ Python O(n) O(h) Easy
0699 Falling Squares C++ Python O(nlogn) O(n) Hard Segment Tree
0700 Search in a Binary Search Tree C++ Python O(h) O(1) Easy Tree
0701 Insert into a Binary Search Tree C++ Python O(h) O(1) Medium Tree
0814 Binary Tree Pruning C++ Python O(n) O(h) Medium DFS
0850 Rectangle Area II C++ Python O(nlogn) O(n) Hard Segment Tree
0863 All Nodes Distance K in Binary Tree C++ Python O(n) O(n) Medium DFS + BFS
0865 Smallest Subtree with all the Deepest Nodes C++ Python O(n) O(h) Medium DFS
0889 Construct Binary Tree from Preorder and Postorder Traversal C++ Python O(n) O(h) Medium DFS, Stack
0897 Increasing Order Search Tree C++ Python O(n) O(h) Easy DFS
0919 Complete Binary Tree Inserter C++ Python ctor: O(n)
insert: O(1)
get_root: O(1)
O(n) Medium
0938 Range Sum of BST C++ Python O(n) O(h) Medium DFS
0951 Flip Equivalent Binary Trees C++ Python O(n) O(h) Medium DFS
0958 Check Completeness of a Binary Tree C++ Python O(n) O(w) Medium BFS
0965 Univalued Binary Tree C++ Python O(n) O(h) Easy DFS
0971 Flip Binary Tree To Match Preorder Traversal C++ Python O(n) O(h) Medium DFS
0979 Distribute Coins in Binary Tree C++ Python O(n) O(h) Medium DFS
0987 Vertical Order Traversal of a Binary Tree C++ Python O(nlogn) O(n) Medium DFS
0988 Smallest String Starting From Leaf C++ Python O(n + l * h) O(h) Medium DFS
0993 Cousins in Binary Tree C++ Python O(n) O(h) Easy DFS
0998 Maximum Binary Tree II C++ Python O(h) O(1) Medium Cartesian Tree


Hash Table

# Title Solution Time Space Difficulty Tag Note
0001 Two Sum C++ Python O(n) O(n) Easy
0003 Longest Substring Without Repeating Characters C++ Python O(n) O(1) Medium
0030 Substring with Concatenation of All Words C++ Python O((m + n) * k) O(n * k) Hard
0036 Valid Sudoku C++ Python O(9^2) O(9) Easy
0049 Group Anagrams C++ Python O(n * glogg) O(n) Medium
0076 Minimum Window Substring C++ Python O(n) O(k) Hard
0149 Max Points on a Line C++ Python O(n^2) O(n) Hard
0159 Longest Substring with At Most Two Distinct Characters C++ Python O(n) O(1) Hard πŸ”’
0170 Two Sum III - Data structure design C++ Python O(n) O(n) Easy πŸ”’
0187 Repeated DNA Sequences Python O(n) O(n) Medium
0202 Happy Number C++ Python O(k) O(k) Easy
0204 Count Primes C++ Python O(n) O(n) Easy Linear Sieve of Eratosthenes
0205 Isomorphic Strings C++ Python O(n) O(1) Easy
0217 Contains Duplicate C++ Python O(n) O(n) Easy
0219 Contains Duplicate II C++ Python O(n) O(n) Easy
0244 Shortest Word Distance II C++ Python ctor: O(n), lookup: O(a + b) O(n) Medium πŸ”’
0246 Strobogrammatic Number C++ Python O(n) O(1) Easy πŸ”’
0249 Group Shifted Strings C++ Python O(nlogn) O(n) Easy πŸ”’
0266 Palindrome Permutation C++ Python O(n) O(1) Easy πŸ”’
0288 Unique Word Abbreviation C++ Python ctor: O(n), lookup: O(1) O(k) Easy πŸ”’
0290 Word Pattern C++ Python O(n) O(c) Easy variant of Isomorphic Strings
0299 Bulls and Cows C++ Python O(n) O(1) Easy
0305 Number of Islands II C++ Python O(k) O(k) Hard LintCode, πŸ”’ Union Find
0314 Binary Tree Vertical Order Traversal C++ Python O(n) O(n) Medium πŸ”’ BFS
0323 Number of Connected Components in an Undirected Graph C++ Python O(n) O(n) Medium πŸ”’ Union Find
0325 Maximum Size Subarray Sum Equals k C++ Python O(n) O(n) Medium πŸ”’
0336 Palindrome Pairs C++ Python O(n * k^2) O(n * k) Hard
0340 Longest Substring with At Most K Distinct Characters C++ Python O(n) O(1) Hard πŸ”’
0356 Line Reflection C++ Python O(n) O(n) Medium πŸ”’ Hash, Two Pointers
0387 First Unique Character in a String C++ Python O(n) O(n) Easy
0388 Longest Absolute File Path C++ Python O(n) O(d) Medium Stack
0409 Longest Palindrome C++ Python O(n) O(1) Easy
0438 Find All Anagrams in a String C++ Python O(n) O(1) Easy
0447 Number of Boomerangs C++ Python O(n^2) O(n) Easy
0454 4Sum II C++ Python O(n^2) O(n^2) Medium
0473 Matchsticks to Square C++ Python O(n * s * 2^n) O(n * (2^n + s)) Medium
0523 Continuous Subarray Sum C++ Python O(n) O(k) Medium
0532 K-diff Pairs in an Array C++ Python O(n) O(n) Easy
0554 Brick Wall C++ Python O(n) O(m) Medium
0560 Subarray Sum Equals K C++ Python O(n) O(n) Medium
0561 Array Partition I C++ Python O(r) O(r) Easy
0575 Distribute Candies C++ Python O(n) O(n) Easy
0594 Longest Harmonious Subsequence C++ Python O(n) O(n) Easy
0599 Minimum Index Sum of Two Lists C++ Python O((m + n) * l) O(m * l) Easy
0609 Find Duplicate File in System C++ Python O(n * l) O(n * l) Medium
0721 Accounts Merge C++ Python O(nlogn) O(n) Medium Union Find
0734 Sentence Similarity C++ Python O(n + p) O(p) Easy
0737 Sentence Similarity II C++ Python O(n + p) O(p) Medium Union Find
0748 Shortest Completing Word C++ Python O(n) O(1) Easy
0760 Find Anagram Mappings C++ Python O(n) O(n) Easy
0771 Jewels and Stones C++ Python O(m + n) O(n) Easy
0811 Subdomain Visit Count C++ Python O(n) O(n) Easy
0822 Card Flipping Game C++ Python O(n) O(n) Medium
0825 Friends Of Appropriate Ages C++ Python O(a^2 + n) O(a) Medium
0869 Reordered Power of 2 C++ Python O(1) O(1) Medium
0873 Length of Longest Fibonacci Subsequence C++ Python O(n^2) O(n) Medium
0957 Prison Cells After N Days C++ Python O(1) O(1) Medium
0966 Vowel Spellchecker C++ Python O(n) O(w) Medium
0974 Subarray Sums Divisible by K C++ Python O(n) O(k) Medium variant of Subarray Sum Equals K
0982 Triples with Bitwise AND Equal To Zero C++ Python O(nlogn) O(n) Hard Math, Fast Wavelet Transform (FWT)


Math

# Title Solution Time Space Difficulty Tag Note
0007 Reverse Integer C++ Python O(1) O(1) Easy
0009 Palindrome Number C++ Python O(1) O(1) Easy
0012 Integer to Roman C++ Python O(n) O(1) Medium
0013 Roman to Integer C++ Python O(n) O(1) Easy
0029 Divide Two Integers C++ Python O(1) O(1) Medium
0050 Pow(x, n) C++ Python O(1) O(1) Medium
0060 Permutation Sequence C++ Python O(n^2) O(n) Medium Cantor Ordering
0065 Valid Number C++ Python O(n) O(1) Hard Automata
0089 Gray Code C++ Python O(2^n) O(1) Medium
0166 Fraction to Recurring Decimal C++ Python O(logn) O(1) Medium
0168 Excel Sheet Column Title C++ Python O(logn) O(1) Easy
0171 Excel Sheet Column Number C++ Python O(n) O(1) Easy
0172 Factorial Trailing Zeroes C++ Python O(1) O(1) Easy
0223 Rectangle Area C++ Python O(1) O(1) Easy
0233 Number of Digit One C++ Python O(1) O(1) Hard CTCI, LintCode
0248 Strobogrammatic Number III C++ Python O(5^(n/2)) O(n) Hard πŸ”’
0258 Add Digits C++ Python O(1) O(1) Easy
0263 Ugly Number C++ Python O(1) O(1) Easy
0292 Nim Game C++ Python O(1) O(1) Easy LintCode
0319 Bulb Switcher C++ Python O(1) O(1) Medium
0326 Power of Three C++ Python O(1) O(1) Easy
0335 Self Crossing C++ Python O(n) O(1) Hard
0338 Counting Bits C++ Python O(n) O(n) Medium
0343 Integer Break C++ Python O(logn) O(1) Medium Tricky, DP
0365 Water and Jug Problem C++ Python O(logn) O(1) Medium BΓ©zout's identity
0372 Super Pow C++ Python O(n) O(1) Medium
0382 Linked List Random Node C++ Python O(n) O(1) Medium Reservoir Sampling
0386 Lexicographical Numbers C++ Python O(n) O(1) Medium
0390 Elimination Game C++ Python O(logn) O(1) Medium
0391 Perfect Rectangle C++ Python O(n) O(n) Hard
0398 Random Pick Index C++ Python O(n) O(1) Medium Reservoir Sampling
0400 Nth Digit C++ Python O(logn) O(1) Easy
0413 Arithmetic Slices C++ Python O(n) O(1) Medium
0423 Reconstruct Original Digits from English C++ Python O(n) O(1) Medium GCJ2016 - Round 1B
0441 Arranging Coins C++ Python O(nlogn) O(1) Easy Binary Search
0453 Minimum Moves to Equal Array Elements C++ Python O(n) O(1) Easy
0458 Poor Pigs C++ Python O(n) O(1) Easy
0469 Convex Polygon C++ Python O(n) O(1) Medium πŸ”’
0470 Implement Rand10() Using Rand7() C++ Python O(1) O(1) Medium
0478 Generate Random Point in a Circle C++ Python O(1) O(1) Medium
0479 Largest Palindrome Product C++ Python O(n * 10^N) O(n) Hard Math
0483 Smallest Good Base C++ Python O(logn * log(logn)) O(1) Hard Math
0492 Construct the Rectangle C++ Python O(1) O(1) Easy Math
0497 Random Point in Non-overlapping Rectangles C++ Python ctor: O(n)
pick: O(logn)
O(n) Medium
0504 Base 7 C++ Python O(n1) O(1) Easy Math
0507 Perfect Number C++ Python O(sqrt(n)) O(1) Easy Math
0517 Super Washing Machines C++ Python O(n) O(1) Hard
0519 Random Flip Matrix C++ Python ctor: O(1)
pick: O(1) reset: O(n)
O(n) Medium
0528 Random Pick with Weight C++ Python ctor: O(n)
pick: O(logn)
O(n) Medium
0537 Complex Number Multiplication C++ Python O(1) O(1) Medium
0553 Optimal Division C++ Python O(n) O(1) Medium
0573 Squirrel Simulation C++ Python O(n) O(1) Medium πŸ”’
0592 Fraction Addition and Subtraction C++ Python O(nlogx) O(n) Medium
0593 Valid Square C++ Python O(1) O(1) Medium
0598 Range Addition II C++ Python O(p) O(1) Easy
0625 Minimum Factorization C++ Python O(loga) O(1) Medium πŸ”’
0628 Maximum Product of Three Numbers C++ Python O(n) O(1) Easy
0633 Sum of Square Numbers C++ Python O(sqrt(c) * logc) O(1) Easy
0634 Find the Derangement of An Array C++ Python O(n) O(1) Medium πŸ”’
0640 Solve the Equation C++ Python O(n) O(n) Medium
0651 4 Keys Keyboard C++ Python O(1) O(1) Medium πŸ”’ Math, DP
0660 Remove 9 C++ Python O(logn) O(1) Hard πŸ”’
0672 Bulb Switcher II C++ Python O(1) O(1) Medium
0728 Self Dividing Numbers C++ Python O(n) O(1) Medium
0754 Reach a Number C++ Python O(logn) O(1) Medium
0775 Global and Local Inversions C++ Python O(n) O(1) Medium
0779 K-th Symbol in Grammar C++ Python O(1) O(1) Medium
0780 Reaching Points C++ Python O(log(max(m, n))) O(1) Hard
0781 Rabbits in Forest C++ Python O(n) O(n) Medium
0782 Transform to Chessboard C++ Python O(n^2) O(n) Hard
0789 Escape The Ghosts C++ Python O(n) O(1) Medium
0800 Similar RGB Color C++ Python O(1) O(1) Easy πŸ”’
0810 Chalkboard XOR Game C++ Python O(1) O(1) Hard
0812 Largest Triangle Area C++ Python O(n^3) O(1) Easy
0829 Consecutive Numbers Sum C++ Python O(sqrt(n)) O(1) Medium
0836 Rectangle Overlap C++ Python O(1) O(1) Easy
0858 Mirror Reflection C++ Python O(1) O(1) Medium
0866 Prime Palindrome C++ Python O(n^(1/2) * (logn + n^(1/2))) O(logn) Medium
0883 Projection Area of 3D Shapes C++ Python O(n^2) O(1) Easy
0887 Super Egg Drop C++ Python O(klogn) O(1) Hard
0891 Sum of Subsequence Widths C++ Python O(n) O(1) Hard
0899 Orderly Queue C++ Python O(n^2) O(n) Hard
0902 Numbers At Most N Given Digit Set C++ Python O(logn) O(logn) Hard
0906 Super Palindromes C++ Python O(n^0.25 * logn) O(logn) Hard
0907 Sum of Subarray Minimums C++ Python O(n) O(n) Medium Mono Stack
0908 Smallest Range I C++ Python O(n) O(1) Easy
0910 Smallest Range II C++ Python O(nlogn) O(1) Medium
0914 X of a Kind in a Deck of Cards C++ Python O(n * (logn)^2) O(n) Easy
0963 Minimum Area Rectangle II C++ Python O(n^2) ~ O(n^3) O(n^2) Medium
0970 Powerful Integers C++ Python O((logn)^2) O(r) Easy
0972 Equal Rational Numbers C++ Python O(1) O(1) Hard


Sort

# Title Solution Time Space Difficulty Tag Note
0056 Merge Intervals C++ Python O(nlogn) O(1) Hard
0057 Insert Interval C++ Python O(n) O(1) Hard
0075 Sort Colors C++ Python O(n) O(1) Medium Tri Partition
0088 Merge Sorted Array C++ Python O(n) O(1) Easy
0147 Insertion Sort List C++ Python O(n^2) O(1) Medium
0148 Sort List C++ Python O(nlogn) O(logn) Medium
0164 Maximum Gap C++ Python O(n) O(n) Hard Tricky
0179 Largest Number C++ Python O(nlogn) O(1) Medium
0218 The Skyline Problem C++ Python O(nlogn) O(n) Hard Sort, BST
0252 Meeting Rooms C++ Python O(nlogn) O(n) Easy πŸ”’
0253 Meeting Rooms II C++ Python O(nlogn) O(n) Medium πŸ”’
0274 H-Index C++ Python O(n) O(n) Medium Counting Sort
0280 Wiggle Sort C++ Python O(n) O(1) Medium πŸ”’
0324 Wiggle Sort II C++ Python O(n) on average O(1) Medium variant of Sort Colors Quick Select, Tri Partition
0347 Top K Frequent Elements C++ Python O(n) O(n) Medium Quick Select, Heap, Bucket Sort
0406 Queue Reconstruction by Height C++ Python O(n * sqrt(n)) O(n) Medium Tricky
0451 Sort Characters By Frequency C++ Python O(n) O(n) Medium
0493 Reverse Pairs C++ Python O(nlogn) O(n) Hard Sort
0692 Top K Frequent Words C++ Python O(n + klogk) on average O(n) Medium Quick Select, Heap, Bucket Sort
0912 Sort an Array C++ Python O(nlogn) O(n) Medium Merge Sort, Quick Sort
0937 Reorder Log Files C++ Python O(nlogn * l) O(l) Easy
0969 Pancake Sorting C++ Python O(nlogn) O(n) Medium variant of Count of Smaller Numbers After Self BIT, Fenwick Tree, Merge Sort
0973 K Closest Points to Origin C++ Python O(n) on average O(1) Easy Quick Select, Heap
0976 Largest Perimeter Triangle C++ Python O(nlogn) O(1) Easy


Two Pointers

# Title Solution Time Space Difficulty Tag Note
0015 3 Sum C++ Python O(n^2) O(1) Medium Two Pointers
0016 3 Sum Closest C++ Python O(n^2) O(1) Medium Two Pointers
0018 4 Sum C++ Python O(n^3) O(1) Medium Two Pointers
0019 Remove Nth Node From End of List C++ Python O(n) O(1) Medium
0086 Partition List C++ Python O(n) O(1) Medium
0141 Linked List Cycle C++ Python O(n) O(1) Easy
0142 Linked List Cycle II C++ Python O(n) O(1) Medium
0143 Reorder List C++ Python O(n) O(1) Medium
0167 Two Sum II - Input array is sorted C++ Python O(n) O(1) Medium
0209 Minimum Size Subarray Sum C++ Python O(n) O(1) Medium Binary Search, Sliding Window
0259 3Sum Smaller C++ Python O(n^2) O(1) Medium πŸ”’, LintCode
0283 Move Zeroes C++ Python O(n) O(1) Easy
0287 Find the Duplicate Number C++ Python O(n) O(1) Hard Binary Search, Two Pointers
0344 Reverse String C++ Python O(n) O(1) Easy
0345 Reverse Vowels of a String C++ Python O(n) O(1) Easy
0349 Intersection of Two Arrays C++ Python O(m + n) O(min(m, n)) Easy EPI Hash, Binary Search
0350 Intersection of Two Arrays II C++ Python O(m + n) O(1) Easy EPI Hash, Binary Search
0360 Sort Transformed Array C++ Python O(n) O(1) Medium πŸ”’
0424 Longest Repeating Character Replacement C++ Python O(n) O(1) Medium Sliding Window
0457 Circular Array Loop C++ Python O(n) O(1) Medium
0567 Permutation in String C++ Python O(n) O(1) Medium
0611 Valid Triangle Number C++ Python O(n^2) O(1) Medium
0777 Swap Adjacent in LR String C++ Python O(n) O(1) Medium
0826 Most Profit Assigning Work C++ Python O(mlogm + nlogn) O(n) Medium
0828 Count Unique Characters of All Substrings of a Given String C++ Python O(n) O(1) Hard
0844 Backspace String Compare C++ Python O(m + n) O(1) Easy
0862 Shortest Subarray with Sum at Least K C++ Python O(n) O(n) Hard Mono Deque, Sliding Window
0876 Middle of the Linked List C++ Python O(n) O(1) Easy
0904 Fruit Into Baskets C++ Python O(n) O(1) Medium Sliding Window
0930 Binary Subarrays With Sum C++ Python O(n) O(1) Medium Sliding Window
0977 Squares of a Sorted Array C++ Python O(n) O(1) Easy
0992 Subarrays with K Different Integers C++ Python O(n) O(k) Hard Two Pointers, Sliding Window


Recursion

# Title Solution Time Space Difficulty Tag Note
0095 Unique Binary Search Trees II C++ Python O(4^n / n^(3/2) O(4^n / n^(3/2) Medium
0098 Validate Binary Search Tree C++ Python O(n) O(1) Medium
0100 Same Tree C+ Python O(n) O(h) Easy
0104 Maximum Depth of Binary Tree C++ Python O(n) O(h) Easy
0105 Construct Binary Tree from Preorder and Inorder Traversal C++ Python O(n) O(n) Medium
0106 Construct Binary Tree from Inorder and Postorder Traversal C++ Python O(n) O(n) Medium
0108 Convert Sorted Array to Binary Search Tree C++ Python O(n) O(logn) Medium
0109 Convert Sorted List to Binary Search Tree C++ Python O(n) O(logn) Medium
0110 Balanced Binary Tree Python O(n) O(h) Easy
0111 Minimum Depth of Binary Tree Python O(n) O(h) Easy
0114 Flatten Binary Tree to Linked List Python O(n) O(h) Medium
0116 Populating Next Right Pointers in Each Node Python O(n) O(1) Medium
0124 Binary Tree Maximum Path Sum C++ Python O(n) O(h) Hard
0129 Sum Root to Leaf Numbers Python O(n) O(h) Medium
0156 Binary Tree Upside Down Python O(n) O(1) Medium πŸ”’
0241 Different Ways to Add Parentheses C++ Python O(n * 4^n / n^(3/2)) O(n * 4^n / n^(3/2)) Medium
0298 Binary Tree Longest Consecutive Sequence C++ Python O(n) O(h) Medium πŸ”’
0327 Count of Range Sum C++ Python O(nlogn) O(n) Hard
0333 Largest BST Subtree C++ Python O(n) O(h) Medium πŸ”’
0337 House Robber III C++ Python O(n) O(h) Medium
0395 Longest Substring with At Least K Repeating Characters C++ Python O(n) O(1) Medium
0404 Sum of Left Leaves C++ Python O(n) O(h) Easy
0437 Path Sum III C++ Python O(n) O(h) Easy
0544 Output Contest Matches C++ Python O(n) O(n) Medium
0549 Binary Tree Longest Consecutive Sequence II C++ Python O(n) O(h) Medium πŸ”’
0669 Trim a Binary Search Tree C++ Python O(n) O(h) Easy
0671 Second Minimum Node In a Binary Tree C++ Python O(n) O(h) Easy
0761 Special Binary String C++ Python O(n^2) O(n) Hard


Binary Search

# Title Solution Time Space Difficulty Tag Note
0004 Median of Two Sorted Arrays C++ Python O(log(min(m, n))) O(1) Hard
0033 Search in Rotated Sorted Array C++ Python O(logn) O(1) Medium CTCI
0034 Find First and Last Position of Element in Sorted Array C++ Python O(logn) O(1) Medium
0035 Search Insert Position C++ Python O(logn) O(1) Medium
0069 Sqrt(x) C++ Python O(logn) O(1) Medium
0074 Search a 2D Matrix C++ Python O(logm + logn) O(1) Medium
0081 Search in Rotated Sorted Array II C++ Python O(logn) ~ O(n) O(1) Medium CTCI
0153 Find Minimum in Rotated Sorted Array C++ Python O(logn) O(1) Medium
0154 Find Minimum in Rotated Sorted Array II C++ Python O(logn) ~ O(n) O(1) Hard
0162 Find Peak Element C++ Python O(logn) O(1) Medium
0222 Count Complete Tree Nodes C++ Python O((logn)^2) O(1) Medium
0275 H-Index II C++ Python O(logn) O(1) Medium Binary Search
0278 First Bad Version C++ Python O(logn) O(1) Easy LintCode
0300 Longest Increasing Subsequence C++ Python O(nlogn) O(n) Medium CTCI, LintCode Binary Search, Segment Tree, DP
0302 Smallest Rectangle Enclosing Black Pixels C++ Python O(nlogn) O(1) Hard πŸ”’
0354 Russian Doll Envelopes C++ Python O(nlogn) O(1) Hard
0363 Max Sum of Rectangle No Larger Than K C++ Python O(min(m, n)^2 * max(m, n) * logn(max(m, n))) O(max(m, n)) Hard
0367 Valid Perfect Square C++ Python O(logn) O(1) Medium
0374 Guess Number Higher or Lower C++ Python O(logn) O(1) Easy
0410 Split Array Largest Sum C++ Python O(nlogs) O(1) Hard
0436 Find Right Interval C++ Python O(nlogn) O(n) Medium
0475 Heaters C++ Python O((m + n) * logn) O(1) Easy
0540 Single Element in a Sorted Array C++ Python O(logn) O(1) Medium
0658 Find K Closest Elements C++ Python O(logn + k) O(1) Medium
0668 Kth Smallest Number in Multiplication Table C++ Python O(m * log(m * n)) O(1) Hard
0702 Search in a Sorted Array of Unknown Size C++ Python O(logn) O(1) Medium πŸ”’ Binary Search
0704 Binary Search C++ Python O(logn) O(1) Easy Binary Search
0710 Random Pick with Blacklist C++ Python ctor: O(b)
pick: O(1)
O(b) Hard
0719 Find K-th Smallest Pair Distance C++ Python O(nlogn + nlogw) O(1) Hard
0744 Find Smallest Letter Greater Than Target C++ Python O(logn) O(1) Easy
0774 Minimize Max Distance to Gas Station C++ Python O(nlogr) O(1) Hard
0786 K-th Smallest Prime Fraction C++ Python O(nlogr) O(1) Hard
0793 Preimage Size of Factorial Zeroes Function C++ Python O((logn)^2) O(1) Hard
0852 Peak Index in a Mountain Array C++ Python O(logn) O(1) Easy
0875 Koko Eating Bananas C++ Python O(nlogr) O(1) Medium
0878 Nth Magical Number C++ Python O(logn) O(1) Hard
0894 All Possible Full Binary Trees C++ Python O(n * 4^n / n^(3/2)) O(n * 4^n / n^(3/2)) Medium
0911 Online Election C++ Python ctor: O(n)
query : O(logn)
O(n) Medium
0981 Time Based Key-Value Store C++ Python set: O(1)
get : O(logn)
O(n) Medium


Binary Search Tree

# Title Solution Time Space Difficulty Tag Note
0220 Contains Duplicate III C++ Python O(nlogk) O(k) Medium
0230 Kth Smallest Element in a BST C++ Python O(max(h, k)) O(min(h, k)) Medium
0235 Lowest Common Ancestor of a Binary Search Tree C++ Python O(h) O(1) Easy EPI
0270 Closest Binary Search Tree Value C++ Python O(h) O(1) Easy πŸ”’
0285 Inorder Successor in BST C++ Python O(h) O(1) Medium πŸ”’
0352 Data Stream as Disjoint Intervals C++ Python O(logn) O(n) Hard
0449 Serialize and Deserialize BST C++ Python O(n) O(h) Medium
0450 Delete Node in a BST C++ Python O(h) O(h) Medium
0530 Minimum Absolute Difference in BST C++ Python O(n) O(h) Easy
0776 Split BST C++ Python O(n) O(h) Medium πŸ”’
0783 Minimum Distance Between BST Nodes C++ Python O(n) O(h) Easy
0510 Inorder Successor in BST II C++ Python O(h) O(1) Medium πŸ”’


Breadth-First Search

# Title Solution Time Space Difficulty Tag Note
0102 Binary Tree Level Order Traversal C++ Python O(n) O(n) Easy
0107 Binary Tree Level Order Traversal II C++ Python O(n) O(n) Easy
0103 Binary Tree Zigzag Level Order Traversal Python O(n) O(n) Medium
0117 Populating Next Right Pointers in Each Node II Python O(n) O(1) Hard
0127 Word Ladder C++ Python O(b^(d/2)) O(w * l) Medium CTCI Bi-BFS
0130 Surrounded Regions C++ Python O(m * n) O(m + n) Medium
0133 Clone Graph Python O(n) O(n) Medium
0207 Course Schedule C++ Python O(|V| + |E|) O(|E|) Medium Topological Sort
0210 Course Schedule II C++ Python O(|V| + |E|) O(|E|) Medium Topological Sort
0261 Graph Valid Tree C++ Python O(|V| + |E|) O(|V| + |E|) Medium πŸ”’
0269 Alien Dictionary C++ Python O(n) O(1) Hard πŸ”’ Topological Sort, BFS, DFS
0286 Walls and Gates C++ Python O(m * n) O(g) Medium πŸ”’
0310 Minimum Height Trees C++ Python O(n) O(n) Medium
0317 Shortest Distance from All Buildings C++ Python O(k * m * n) O(m * n) Hard πŸ”’
0433 Minimum Genetic Mutation C++ Python O(n * b) O(b) Medium
0444 Sequence Reconstruction C++ Python O(n * s) O(n) Medium πŸ”’ Topological Sort
0490 The Maze C++ Python O(max(r, c) * w) O(w) Medium
0499 The Maze III C++ Python O(max(r, c) * wlogw) O(w^2) Hard
0505 The Maze II C++ Python O(max(r, c) * wlogw) O(w) Medium
0542 01 Matrix C++ Python O(m * n) O(1) Medium DP
0666 Path Sum IV C++ Python O(n) O(w) Medium πŸ”’ Topological Sort
0675 Cut Off Trees for Golf Event C++ Python O(t * m * n) O(m * n) Hard A* Search Algorithm
0742 Closest Leaf in a Binary Tree C++ Python O(n) O(n) Medium
0743 Network Delay Time C++ Python O(|E| * log|V|) O(|E|) Medium Dijkstra's Algorithm
0752 Open the Lock C++ Python O(k * n^k + d) O(k * n^k + d) Medium
0773 Sliding Puzzle C++ Python O((m * n) * (m * n)!) O((m * n) * (m * n)!) Hard A* Search Algorithm
0787 Cheapest Flights Within K Stops C++ Python O(|E| * log|V|) O(|E|) Medium Dijkstra's Algorithm
0815 Bus Routes C++ Python O(|E| + |V|) O(|E| + |V|) Hard
0854 K-Similar Strings C++ Python O(n * n!/(c_a!*...*c_z!)) O(n * n!/(c_a!*...*c_z!)) Hard
0864 Shortest Path to Get All Keys C++ Python O(k * r * c + k^3*2^k) O(k*2^k) Hard Dijkstra's Algorithm
0882 Reachable Nodes In Subdivided Graph C++ Python O(|E| * log|V|) O(|E|) Hard Dijkstra's Algorithm
0886 Possible Bipartition C++ Python O(|V| + |E|) O(|V| + |E|) Medium
0913 Cat and Mouse C++ Python O(n^3) O(n^2) Hard MiniMax, Topological Sort
0934 Shortest Bridge C++ Python O(n^2) O(n^2) Medium BFS, DFS
0967 Numbers With Same Consecutive Differences C++ Python O(2^n) O(2^n) Medium
0994 Rotting Oranges C++ Python O(m * n) O(m * n) Easy


Depth-First Search

# Title Solution Time Space Difficulty Tag Note
0112 Path Sum Python O(n) O(h) Easy
0113 Path Sum II Python O(n) O(h) Medium
0199 Binary Tree Right Side View Python O(n) O(h) Medium
0200 Number of Islands C++ Python O(m * n) O(m * n) Medium BFS, DFS, Union Find
0236 Lowest Common Ancestor of a Binary Tree C++ Python O(n) O(h) Medium EPI
0247 Strobogrammatic Number II C++ Python O(n * 5^(n/2)) O(n) Medium πŸ”’
0250 Count Univalue Subtrees C++ Python O(n) O(h) Medium πŸ”’
0257 Binary Tree Paths C++ Python O(n * h) O(h) Easy
0282 Expression Add Operators C++ Python O(4^n) O(n) Hard
0301 Remove Invalid Parentheses C++ Python O(C(n, c)) O(c) Hard
0329 Longest Increasing Path in a Matrix C++ Python O(m * n) O(m * n) Hard DFS, Topological Sort
0339 Nested List Weight Sum C++ Python O(n) O(h) Easy πŸ”’
0364 Nested List Weight Sum II C++ Python O(n) O(h) Medium πŸ”’
0366 Find Leaves of Binary Tree C++ Python O(n) O(h) Medium πŸ”’
0417 Pacific Atlantic Water Flow C++ Python O(m * n) O(m * n) Medium
0440 K-th Smallest in Lexicographical Order C++ Python O(logn) O(logn) Hard
0464 Can I Win C++ Python O(n!) O(n) Medium
0515 Find Largest Value in Each Tree Row C++ Python O(n) O(h) Medium
0547 Friend Circles C++ Python O(n^2) O(n) Medium Union Find
0582 Kill Process C++ Python O(n) O(n) Medium πŸ”’ DFS, BFS
0638 Shopping Offers C++ Python O(n * 2^n) O(n) Medium
0690 Employee Importance C++ Python O(n) O(h) Easy DFS, BFS
0694 Number of Distinct Islands C++ Python O(m * n) O(m * n) Medium πŸ”’
0695 Max Area of Island C++ Python O(m * n) O(m * n) Easy
0711 Number of Distinct Islands II C++ Python O((m * n) * log(m * n)) O(m * n) Hard πŸ”’ Hash
0733 Max Area of Island C++ Python O(m * n) O(m * n) Easy
0749 Contain Virus C++ Python O((m * n)^(4/3)) O(m * n) Hard Simulation
0753 Cracking the Safe C++ Python O(k^n) O(k^n) Hard de Bruijn sequences, Lyndon word, Rolling Hash, Backtracking, Greedy
0756 Pyramid Transition Matrix C++ Python O(a^b) O(a^b) Medium
0785 Is Graph Bipartite? C++ Python O(|V| + |E|) O(|V|) Medium
0797 All Paths From Source to Target C++ Python O(p + r * n) O(n) Medium
0802 Find Eventual Safe States C++ Python O(|V| + |E|) O(|V|) Medium
0827 Making A Large Island C++ Python O(n^2) O(n^2) Hard
0834 Sum of Distances in Tree C++ Python O(n) O(n) Hard
0841 Keys and Rooms C++ Python O(n!) O(n) Medium
0851 Loud and Rich C++ Python O(q + r) O(q + r) Medium


Backtracking

# Title Solution Time Space Difficulty Tag Note
0017 Letter Combinations of a Phone Number C++ Python O(n * 4^n) O(1) Medium
0022 Generate Parentheses C++ Python O(4^n / n^(3/2)) O(n) Medium
0037 Sudoku Solver Python O((9!)^9) O(1) Hard
0039 Combination Sum Python O(k * n^k) O(k) Medium
0040 Combination Sum II Python O(k * C(n, k)) O(k) Medium
0046 Permutations Python O(n * n!) O(n) Medium
0047 Permutations II Python O(n * n!) O(n) Medium
0051 N-Queens Python O(n!) O(n) Hard
0052 N-Queens-II Python O(n!) O(n) Hard
0077 Combinations C++ Python O(O(k * C(n, k))) O(k) Medium
0079 Word Search C++ Python O(m * n * 3^l) O(l) Medium
0093 Restore IP Addresses Python O(1) O(1) Medium
0078 Subsets C++ Python O(n * 2^n) O(1) Medium
0090 Subsets II C++ Python O(n * 2^n) O(1) Medium
0126 Word Ladder II C++ Python O(b^(d/2)) O(w * l) Hard CTCI Bi-BFS
0131 Palindrome Partitioning Python O(n^2) ~ O(2^n) O(n^2) Medium
0140 Word Break II C++ Python O(n * l^2 + n * r) O(n^2) Hard
0212 Word Search II C++ Python O(m * n * 3^h) O(t) Hard LintCode Trie, DFS
0216 Combination Sum III C++ Python O(k * C(n, k)) O(k) Medium
0254 Factor Combinations C++ Python O(nlogn) O(logn) Medium πŸ”’
0267 Palindrome Permutation II C++ Python O(n * n!) O(n) Medium πŸ”’
0291 Word Pattern II C++ Python O(n * C(n - 1, c - 1)) O(n + c) Hard πŸ”’
0294 Flip Game II C++ Python O(n + c^2) O(c) Medium πŸ”’ DP, Hash, Sprague-Grundy Theorem
0320 Generalized Abbreviation C++ Python O(n * 2^n) O(n) Medium πŸ”’
0425 Word Squares C++ Python O(n^2 * n!) O(n^2) Hard πŸ”’
0488 Zuma Game C++ Python O((b+h) * h!*(b+h-1)!/(b-1)!) O((b+h) * h!*(b+h-1)!/(b-1)!) Hard Backtracking
0491 Increasing Subsequences C++ Python O(n * 2^n) O(n) Medium Backtracking
0526 Beautiful Arrangement C++ Python O(n!) O(n) Medium
0676 Implement Magic Dictionary C++ Python O(n) O(d) Medium Trie, DFS
0679 24 Game C++ Python O(1) O(1) Hard DFS
0698 Partition to K Equal Sum Subsets C++ Python O(n * 2^n) O(2^n) Medium DFS, DP, Memoization
0718 Maximum Length of Repeated Subarray C++ Python O(m * n) O(min(m, n)) Medium DP, Hash, Binary Search
0784 Letter Case Permutation C++ Python O(n * 2^n) O(1) Easy
0996 Number of Squareful Arrays C++ Python O(n!) O(n^2) Hard


Dynamic Programming

# Title Solution Time Space Difficulty Tag Note
0010 Regular Expression Matching Python O(m * n) O(n) Hard
0044 Wildcard Matching Python O(m * n) O(1) Hard Greedy
0053 Maximum Subarray C++ Python O(n) O(1) Easy
0062 Unique Paths Python O(m + n) O(1) Medium Combinatorics
0063 Unique Paths II Python O(m * n) O(m + n) Medium
0064 Minimum Path Sum Python O(m * n) O(m + n) Medium
0070 Climbing Stairs C++ Python O(logn) O(1) Easy Matrix Exponentiation
0072 Edit Distance Python O(m * n) O(m + n) Hard
0087 Scramble String Python O(n^4) O(n^3) Hard
0091 Decode Ways C++ Python O(n) O(1) Medium
0096 Unique Binary Search Trees Python O(n) O(1) Medium Math
0097 Interleaving String Python O(m * n) O(m + n) Hard
0115 Distinct Subsequences Python O(n^2) O(n) Hard
0120 Triangle Python O(m * n) O(n) Medium
0123 Best Time to Buy and Sell Stock III Python O(n) O(1) Hard
0132 Palindrome Partitioning II Python O(n^2) O(n^2) Hard
0139 Word Break C++ Python O(n * l^2) O(n) Medium
0152 Maximum Product Subarray C++ Python O(n) O(1) Medium
0174 Dungeon Game Python O(m * n) O(m + n) Hard
0188 Best Time to Buy and Sell Stock IV C++ Python O(n) O(n) Hard Quick Select, Mono Stack
0198 House Robber C++ Python O(n) O(1) Easy
0213 House Robber II C++ Python O(n) O(1) Medium
0221 Maximal Square C++ Python O(n^2) O(n) Medium EPI
0256 Paint House C++ Python O(n) O(1) Medium πŸ”’
0265 Paint House II C++ Python O(n * k) O(k) Hard πŸ”’
0276 Paint Fence C++ Python O(n) O(1) Easy πŸ”’
0279 Perfect Squares C++ Python O(n * sqrt(n)) O(n) Medium Hash
0303 Range Sum Query - Immutable C++ Python ctor: O(n), lookup: O(1) O(n) Easy
0304 Range Sum Query 2D - Immutable C++ Python ctor: O(m * n), lookup: O(1) O(m * n) Medium
0309 Best Time to Buy and Sell Stock with Cooldown C++ Python O(n) O(1) Medium
0312 Burst Balloons C++ Python O(n^3) O(n^2) Hard
0322 Coin Change C++ Python O(n * k) O(k) Medium
0351 Android Unlock Patterns C++ Python O(9^2 * 2^9) O(9 * 2^9) Medium πŸ”’ Backtracking
0357 Count Numbers with Unique Digits C++ Python O(n) O(1) Medium Backtracking, Math
0361 Bomb Enemy C++ Python O(m * n) O(m * n) Medium πŸ”’
0368 Largest Divisible Subset C++ Python O(n^2) O(n) Medium
0375 Guess Number Higher or Lower II C++ Python O(n^3) O(n^2) Medium
0377 Combination Sum IV C++ Python O(nlogn + n * t) O(t) Medium
0403 Frog Jump C++ Python O(n^2) O(n^2) Hard
0416 Partition Equal Subset Sum C++ Python O(n * s) O(s) Medium
0418 Sentence Screen Fitting C++ Python O(r + n * c) O(n) Medium πŸ”’
0446 Arithmetic Slices II - Subsequence C++ Python O(n^2) O(n * d) Hard
0465 Optimal Account Balancing C++ Python O(n * 2^n) O(2^n) Hard πŸ”’
0466 Count The Repetitions C++ Python O(s1 * min(s2, n1)) O(s2) Hard
0467 Unique Substrings in Wraparound String C++ Python O(n) O(1) Medium
0471 Encode String with Shortest Length C++ Python O(n^3) on average O(n^2) Medium πŸ”’
0472 Concatenated Words C++ Python O(n * l^2) O(n * l) Medium
0474 Ones and Zeroes C++ Python O(s * m * n) O(m * n) Medium
0486 Predict the Winner C++ Python O(n^2) O(n) Medium
0494 Target Sum C++ Python O(n * S) O(S) Medium DP
0509 Fibonacci Number C++ Python O(logn) O(1) Easy variant of Climbing Stairs Matrix Exponentiation
0514 Freedom Trail C++ Python O(k) ~ O(k * r^2) O(r) Hard
0516 Longest Palindromic Subsequence C++ Python O(n^2) O(n) Medium
0518 Coin Change 2 C++ Python O(n * m) O(m) Medium DP
0546 Remove Boxes C++ Python O(n^3) ~ O(n^4) O(n^3) Hard
0552 Student Attendance Record II C++ Python O(n) O(1) Hard
0562 Longest Line of Consecutive One in Matrix C++ Python O(m * n) O(n) Medium πŸ”’
0568 Maximum Vacation Days C++ Python O(n^2 * k) O(k) Hard πŸ”’
0576 Out of Boundary Paths C++ Python O(N * m * n) O(m * n) Medium
0583 Delete Operation for Two Strings C++ Python O(m * n) O(n) Medium
0600 Non-negative Integers without Consecutive Ones C++ Python O(1) O(1) Hard
0629 K Inverse Pairs Array C++ Python O(n * k) O(k) Hard
0639 Decode Ways II C++ Python O(n) O(1) Hard
0650 2 Keys Keyboard C++ Python O(sqrt(n)) O(1) Medium
0656 Coin Path C++ Python O(n * B) O(n) Hard πŸ”’
0664 Strange Printer C++ Python O(n^3) O(n^2) Hard
0673 Number of Longest Increasing Subsequence C++ Python O(n^2) O(n) Medium
0688 Knight Probability in Chessboard C++ Python O(k * n^2) O(n^2) Medium
0689 Maximum Sum of 3 Non-Overlapping Subarrays C++ Python O(n) O(n) Hard
0691 Stickers to Spell Word C++ Python O(T * S^T) O(T * S^T) Hard Backtracking, Memoization
0712 Minimum ASCII Delete Sum for Two Strings C++ Python O(m * n) O(n) Medium
0714 Best Time to Buy and Sell Stock with Transaction Fee C++ Python O(n) O(1) Medium
0727 Minimum Window Subsequence C++ Python O(s * t) O(s) Hard πŸ”’
0730 Count Different Palindromic Subsequences C++ Python O(n^2) O(n) Hard
0740 Delete and Earn C++ Python O(n) O(1) Medium
0741 Cherry Pickup C++ Python O(n^3) O(n^2) Hard
0746 Min Cost Climbing Stairs C++ Python O(n) O(1) Easy
0750 Number Of Corner Rectangles C++ Python O(n * m^2) O(n * m) Medium
0764 Largest Plus Sign C++ Python O(n^2) O(n^2) Medium
0788 Rotated Digits C++ Python O(logn) O(logn) Easy Memoization
0790 Domino and Tromino Tiling C++ Python O(logn) O(1) Medium Matrix Exponentiation
0799 Champagne Tower C++ Python O(n^2) O(n) Medium
0801 Minimum Swaps To Make Sequences Increasing C++ Python O(n) O(1) Medium
0805 Split Array With Same Average C++ Python O(n^4) O(n^3) Hard
0808 Soup Servings C++ Python O(1) O(1) Medium Memoization
0813 Largest Sum of Averages C++ Python O(k * n^2) O(n) Medium
0818 Race Car C++ Python O(nlogn) O(n) Hard
0823 Binary Trees With Factors C++ Python O(n^2) O(n) Medium
0837 New 21 Game C++ Python O(n) O(n) Medium
0838 Push Dominoes C++ Python O(n) O(n) Medium
0847 Shortest Path Visiting All Nodes C++ Python O(n *2^n) O(n * 2^n) Hard BFS
0877 Stone Game C++ Python O(n^2) O(n) Medium variant of Predict the Winner
0879 Profitable Schemes C++ Python O(n * p * g) O(p * g) Hard
0903 Valid Permutations for DI Sequence C++ Python O(n^2) O(n) Hard
0920 Number of Music Playlists C++ Python O(n * l) O(l) Hard
0926 Flip String to Monotone Increasing C++ Python O(n) O(1) Medium
0931 Minimum Falling Path Sum C++ Python O(n^2) O(1) Medium
0935 Knight Dialer C++ Python O(logn) O(1) Medium Matrix Exponentiation
0940 Distinct Subsequences II C++ Python O(n) O(1) Hard
0943 Find the Shortest Superstring C++ Python O(n^2 * (l^2 + 2^n)) O(n^2) Hard
0956 Tallest Billboard C++ Python O(n * 3^(n/2)) O(3^(n/2)) Hard
0960 Delete Columns to Make Sorted III C++ Python O(n * l^2) O(l) Hard
0964 Least Operators to Express Number C++ Python O(logn / logx) O(logn) Hard Math
0975 Odd Even Jump C++ Python O(nlogn) O(n) Hard Mono Stack, BST
0980 Unique Paths III C++ Python O((m * n) * 2^(m * n)) O((m * n) * 2^(m * n)) Hard
0983 Minimum Cost For Tickets C++ Python O(n) O(1) Medium
1000 Minimum Cost to Merge Stones C++ Python O(n^3 / k) O(n^2) Hard


Greedy

# Title Solution Time Space Difficulty Tag Note
0011 Container With Most Water C++ Python O(n) O(1) Medium
0042 Trapping Rain Water C++ Python O(n) O(1) Hard Tricky
0045 Jump Game II Python O(n) O(1) Hard
0055 Jump Game C++ Python O(n) O(1) Medium
0122 Best Time to Buy and Sell Stock II C++ Python O(n) O(1) Easy
0134 Gas Station Python O(n) O(1) Medium
0135 Candy C++ Python O(n) O(n) Hard
0316 Remove Duplicate Letters C++ Python O(n) O(1) Hard Mono Stack
0321 Create Maximum Number C++ Python O(k * (m + n + k)) ~ O(k * (m + n + k^2)) O(m + n + k^2) Hard variant of Delete Digits Greedy, DP
0330 Patching Array C++ Python O(s + logn) O(1) Hard
0376 Wiggle Subsequence C++ Python O(n) O(1) Medium
0392 Is Subsequence C++ Python O(n) O(1) Medium
0397 Integer Replacement C++ Python O(n) O(1) Medium Math
0402 Remove K Digits C++ Python O(n) O(n) Medium LintCode
0435 Non-overlapping Intervals C++ Python O(nlogn) O(1) Medium Line Sweep
0452 Minimum Number of Arrows to Burst Balloons C++ Python O(nlogn) O(1) Medium
0455 Assign Cookies C++ Python O(nlogn) O(1) Easy
0484 Find Permutation C++ Python O(n) O(1) Medium πŸ”’
0621 Task Scheduler C++ Python O(n) O(1) Medium
0630 Course Schedule III C++ Python O(nlogn) O(k) Hard
0646 Maximum Length of Pair Chain C++ Python O(nlogn) O(1) Medium variant of Non-overlapping Intervals Line Sweep
0649 Dota2 Senate C++ Python O(n) O(n) Medium
0659 Split Array into Consecutive Subsequences C++ Python O(n) O(1) Medium
0738 Monotone Increasing Digits C++ Python O(1) O(1) Medium
0757 Set Intersection Size At Least Two C++ Python O(nlogn) O(n) Hard
0759 Employee Free Time C++ Python O(m * logn) O(n) Hard
0763 Partition Labels C++ Python O(n) O(n) Medium
0767 Reorganize String C++ Python O(n) O(1) Medium
0798 Smallest Rotation with Highest Score C++ Python O(n) O(1) Hard
0843 Guess the Word C++ Python O(n) O(n) Hard MinMax, Math
0861 Score After Flipping Matrix C++ Python O(r * c) O(1) Medium
0870 Advantage Shuffle C++ Python O(nlogn) O(n) Medium
0881 Boats to Save People C++ Python O(nlogn) O(n) Medium
0936 Stamping The Sequence C++ Python O((n - m) * m) O((n - m) * m) Hard
0948 Bag of Tokens C++ Python O(nlogn) O(1) Medium Two Pointers
0962 Maximum Width Ramp C++ Python O(n) O(n) Medium Mono Stack
0968 Binary Tree Cameras C++ Python O(n) O(h) Hard DFS
0984 String Without AAA or BBB C++ Python O(a + b) O(1) Easy
0991 Broken Calculator C++ Python O(logn) O(1) Medium
0995 Minimum Number of K Consecutive Bit Flips C++ Python O(n) O(1) Hard


Graph

# Title Solution Time Space Difficulty Tag Note
0332 Reconstruct Itinerary C++ Python O(|V| + |E|log|V|) O(|V| + |E|) Medium Hierholzer's Algorithm, Eulerian Path
0399 Evaluate Division C++ Python O(e + q) O(e) Medium Floyd-Warshall Algorithm, BFS, Union Find
0765 Couples Holding Hands C++ Python O(n) O(n) Hard
0924 Minimize Malware Spread C++ Python O(n^2) O(n) Hard Union Find
0928 Minimize Malware Spread II C++ Python O(n^2) O(n) Hard Union Find
0959 Regions Cut By Slashes C++ Python O(n^2) O(n^2) Medium Union Find
0990 Satisfiability of Equality Equations C++ Python O(n) O(1) Medium Union Find


Geometry

# Title Solution Time Space Difficulty Tag Note
0587 Erect the Fence C++ Python O(nlogn) O(n) Hard Convex Hull, Monotone Chain
0892 Surface Area of 3D Shapes C++ Python O(n^2) O(1) Easy


Simulation

# Title Solution Time Space Difficulty Tag Note
0874 Walking Robot Simulation C++ Python O(n + k) O(k) Easy


Design

# Title Solution Time Space Difficulty Tag Note
0146 LRU Cache C++ Python O(1) O(k) Hard OrderedDict
0225 Implement Stack using Queues C++ Python push: O(n), pop: O(1), top: O(1) O(n) Easy
0173 Binary Search Tree Iterator C++ Python O(1), amortized O(h) Medium
0284 Peeking Iterator C++ Python O(1) O(1) Medium
0348 Design Tic-Tac-Toe C++ Python O(1) O(n^2) Medium πŸ”’
0353 Design Snake Game C++ Python O(1) O(s) Medium πŸ”’ Deque
0355 Design Twitter C++ Python O(klogu) O(t + f) Medium LintCode Heap
0359 Logger Rate Limiter C++ Python O(1), amortized O(k) Easy πŸ”’ Deque
0362 Design Hit Counter C++ Python O(1), amortized O(k) Medium πŸ”’ Deque
0379 Design Phone Directory C++ Python O(1) O(n) Medium πŸ”’
0380 Insert Delete GetRandom O(1) C++ Python O(1) O(n) Hard
0381 Insert Delete GetRandom O(1) - Duplicates allowed C++ Python O(1) O(n) Hard
0432 All O`one Data Structure C++ Python O(1) O(n) Hard
0460 LFU Cache C++ Python O(1) O(k) Hard
0489 Robot Room Cleaner C++ Python O(n) O(n) Hard πŸ”’
0535 Encode and Decode TinyURL C++ Python O(1) O(n) Medium
0588 Design In-Memory File System C++ Python ls: O(l + klogk)
mkdir: O(l)
addContentToFile: O(l + c)
readContentFromFile: O(l + c)
O(n + s) Hard πŸ”’
0604 Design Compressed String Iterator C++ Python O(1) O(1) Easy πŸ”’
0622 Design Circular Queue C++ Python O(1) O(k) Medium Design
0631 Design Excel Sum Formula C++ Python set: O((r * c)^2)
get: O(1)
sum: O((r * c)^2)
O(r * c) Hard πŸ”’
0635 Design Log Storage System C++ Python put: O(1)
retrieve: O(n + dlogd)
O(n) Medium πŸ”’
0641 Design Circular Deque C++ Python O(1) O(1) Medium Design
0642 Design Search Autocomplete System C++ Python O(p^2) O(p * t + s) Hard πŸ”’
0705 Design HashSet C++ Python O(1) O(n) Easy Design
0706 Design HashMap C++ Python O(1) O(n) Easy Design
0707 Design Linked List C++ Python O(n) O(n) Medium Design
0715 Range Module C++ Python add: O(n)
remove: O(n)
query: O(logn)
O(n) Hard
0716 Max Stack C++ Python push: O(logn)
pop: O(logn)
popMax: O(logn)
top: O(1)
peekMax: O(1)
O(n) Easy
0745 Prefix and Suffix Search C++ Python ctor: O(w * l^2)
search : O(p + s)
O(t) Hard Trie
0900 RLE Iterator C++ Python O(n) O(1) Medium


Concurrency

# Title Solution Time Space Difficulty Tag Note


SQL

# Title Solution Time Space Difficulty Tag Note
0175 Combine Two Tables MySQL O(m + n) O(m + n) Easy
0176 Second Highest Salary MySQL O(n) O(1) Easy
0177 Nth Highest Salary MySQL O(n^2) O(n) Medium
0178 Rank Scores MySQL O(n^2) O(n) Medium
0180 Consecutive Numbers MySQL O(n) O(n) Medium
0181 Employees Earning More Than Their Managers MySQL O(n^2) O(1) Easy
0182 Duplicate Emails MySQL O(n^2) O(n) Easy
0183 Customers Who Never Order MySQL O(n^2) O(1) Easy
0184 Department Highest Salary MySQL O(n^2) O(n) Medium
0185 Department Top Three Salaries MySQL O(n^2) O(n) Hard
0196 Delete Duplicate Emails MySQL O(n^2) O(n) Easy
0197 Rising Temperature MySQL O(n^2) O(n) Easy
0262 Trips and Users MySQL O((t * u) + tlogt) O(t) Hard
0511 Game Play Analysis I MySQL O(n) O(n) Easy πŸ”’
0512 Game Play Analysis II MySQL O(n) O(n) Easy πŸ”’
0534 Game Play Analysis III MySQL O(nlogn) O(n) Medium πŸ”’
0550 Game Play Analysis IV MySQL O(n) O(n) Medium πŸ”’
0569 Median Employee Salary MySQL O(nlogn) O(n) Hard πŸ”’
0570 Managers with at Least 5 Direct Reports MySQL O(n) O(n) Medium πŸ”’
0571 Find Median Given Frequency of Numbers MySQL O(nlogn) O(n) Hard πŸ”’
0574 Winning Candidate MySQL O(nlogn) O(n) Medium πŸ”’
0577 Employee Bonus MySQL O(n) O(n) Easy πŸ”’
0578 Get Highest Answer Rate Question MySQL O(nlogn) O(n) Medium πŸ”’
0579 Find Cumulative Salary of an Employee MySQL O(n^2) O(n) Hard πŸ”’
0580 Count Student Number in Departments MySQL O(s + dlogd) O(s + d) Medium πŸ”’
0584 Find Customer Referee MySQL O(n) O(1) Easy πŸ”’
0585 Investments in 2016 MySQL O(n^2) O(n) Medium πŸ”’
0586 Customer Placing the Largest Number of Orders MySQL O(n) O(n) Easy πŸ”’
0595 Big Countries MySQL O(n) O(1) Easy
0596 Classes More Than 5 Students MySQL O(n) O(n) Easy
0597 Friend Requests I: Overall Acceptance Rate MySQL O(rlogr + aloga) O(r + a) Easy πŸ”’
0601 Human Traffic of Stadium MySQL O(n^3) O(n^3) Hard
0602 Friend Requests II: Who Has the Most Friends MySQL O(nlogn) O(n) Medium πŸ”’
0603 Consecutive Available Seats MySQL O(nlogn) O(n) Easy πŸ”’
0607 Sales Person MySQL O(s * o) O(s + o) Easy πŸ”’
0608 Tree Node MySQL O(n^2) O(n) Medium πŸ”’
0610 Triangle Judgement MySQL O(n) O(1) Easy πŸ”’
0612 Shortest Distance in a Plane MySQL O(n^2) O(n^2) Medium πŸ”’
0613 Shortest Distance in a Line MySQL O(nlogn) O(n) Easy πŸ”’
0614 Second Degree Follower MySQL O(nlogn) O(n) Medium πŸ”’
0615 Average Salary: Departments VS Company MySQL O(nlogn) O(n) Hard πŸ”’
0618 Students Report By Geography MySQL O(nlogn) O(n) Hard πŸ”’
0619 Biggest Single Number MySQL O(n) O(n) Easy πŸ”’
0620 Not Boring Movies MySQL O(nlogn) O(1) Easy
0626 Exchange Seats MySQL O(nlogn) O(n) Medium
0627 Swap Salary MySQL O(n) O(1) Easy


Shell Script

# Title Solution Time Space Difficulty Tag Note
0192 Word Frequency Shell O(n) O(k) Medium
0193 Valid Phone Numbers Shell O(n) O(1) Easy
0194 Transpose File Shell O(n^2) O(n^2) Medium
0195 Tenth Line Shell O(n) O(1) Easy