Problems Solved: 416
Easy: 153 | Medium: 225 | Hard: 38
| # | Title | Category | Difficulty | Solution | Time | Space |
|---|---|---|---|---|---|---|
| 1528 | Shuffle String | Sort | Easy | python, c++ | O(N) | O(N) |
| 350 | Intersection of Two Arrays II | Hash Table, Two Pointer, Binary Search | Easy | python | O(N) | O(N) |
| 206 | Reverse Linked List | Linked List, Recursion | Easy | python, c++ | O(N) | O(1) |
| 1640 | Check Array Formation Through Concatenation | Array, Hash Table, Sort | Easy | python | O(N) | O(N) |
| 957 | Prison Cells After N Days | Hash Table | Medium | python, c++ | O(1) | O(1) |
| 1502 | Can Make Arithmetic Progression From Sequence | Arrya, Sort | Easy | python | O(NlogN) | O(1) |
| 242 | Valid Anagram | Hash Table, Sort | Easy | python | O(N) | O(1) |
| 1450 | Number of Students Doing Homework at a Given Time | Array | Easy | python | O(N) | O(1) |
| 1600 | Throne Inheritance | Tree, Design | Medium | python | O(N) | O(N^2) |
| 1742 | Maximum Number of Balls in a Box | Array | Easy | python | O(N) | O(1) |
| 1054 | Distant Barcodes | Heap, Sort | Medium | python | O(N) | O(N) |
| 1464 | Maximum Product of Two Elements in an Array | Array | Easy | python | O(N) | O(1) |
| 1725 | Number Of Rectangles That Can Form The Largest Square | Greedy | Easy | python | O(N) | O(N) |
| 452 | Minimum Number of Arrows to Burst Balloons | Greedy, Sort | Medium | python | O(NlogN) | O(1) |
| 1403 | Minimum Subsequence in Non-Increasing Order | Greedy, Sort | Easy | python | O(N) | O(1) |
| 1665 | Minimum Initial Energy to Finish Tasks | Greedy | Hard | python | O(NlogN) | O(1) |
| 455 | Assign Cookies | Greedy | Easy | python, c++ | O(NlogN) | O(1) |
| 1138 | Alphabet Board Path | Hash Table, String | Medium | python, c++ | O(N) | O(1) |
| 852 | Peak Index in a Mountain Array | Binary Search | Easy | python | O(logN) | O(1) |
| 1207 | Unique Number of Occurrences | Hash Table | Easy | python | O(N) | O(N) |
| 1122 | Relative Sort Array | Array, Sort | Easy | python, c++ | O(NM) | O(N) |
| 1160 | Find Words That Can Be Formed by Characters | Array, Hash Table | Easy | python, c++ | O(N*M) | O(1) |
| 1031 | Maximum Sum of Two Non-Overlapping Subarrays | Array | Medium | python | O(N) | O(1) |
| 1491 | Average Salary Excluding the Minimum and Maximum Salary | Array, Sort | Easy | python | O(N) | O(1) |
| 283 | Move Zeroes | Array, Two Pointers | Easy | C++, python | O(N) | O(1) |
| 445 | Add Two Numbers II | Linked List | Medium | python | O(N) | O(N) |
| 2 | Add Two Numbers | Linked List | Medium | python, c++ | O(N) | O(1) |
| 1254 | Number of Closed Islands | Depth-first Search | Medium | python | O(NM) | O(1) |
| 1507 | Reformat Date | String | Easy | python | O(1) | O(1) |
| 721 | Accounts Merge | Depth-first Search, Union Find | Medium | python | O(NM) | O(NM) |
| 1103 | Distribute Candies to People | Math | Easy | python | O(N) | O(N) |
| 202 | Happy Number | Hash Table, Math | Easy | python, c | O(1) | O(1) |
| 1710 | Maximum Units on a Truck | Greedy, Hash, Sort | Easy | python | O(N) | O(1) |
| 1 | Two Sum | Array, Hash | Easy | c, c++ | O(N) | O(N) |
| 9 | Palindrome Number | Math | Easy | python | O(N) | O(N) |
| 35 | Search Insert Position | Array, Binary Search | Easy | python | O(logN) | O(1) |
| 66 | Plus One | Array, Math | Easy | python | O(N) | O(N) |
| 83 | Remove Duplicates from Sorted List | Linked List | Easy | python | O(N) | O(1) |
| 94 | Binary Tree Inorder Traversal | Stack, Tree, DFS, Binary Tree | Easy | python | O(N) | O(N) |
| 13 | Roman to Integer | Hash Table, Math, String | Easy | C++ | O(N) | O(1) |
| 26 | Remove Duplicates from Sorted Array | Array, Two Pointers | Easy | python, c++ | O(N) | O(1) |
| 122 | Best Time to Buy and Sell Stock II | Array, Dynamic Programming, Gredy | Medium | python | O(N) | O(N) |
| 136 | Single Number | Array, Bit Manipulation | Easy | c | O(N) | O(1) |
| 15 | 3Sum | Array, Two Pointer, Sorting | Medium | python, c++ | O(N^2) | O(N) |
| 169 | Majority Element | Array, Hash Table, Divide and Conquer | Easy | python, c++ | O(N) | O(1) |
| 1470 | Running Sum of 1d Array | Array | Easy | python | O(N) | O(1) |
| 724 | Find Pivot Index | Array | Easy | python, c++ | O(N) | O(1) |
| 205 | Isomorphic Strings | Array | Easy | python, c++ | O(N) | O(1) |
| 392 | Is Subsequence | Two Pointers, String, Dynamic Programming | Easy | python, c++ | O(N) | O(1) |
| 14 | Longest Common Prefix | String, Trie | Easy | python, c++ | O(M*N) | O(1) |
| 704 | Binary Search | Array, Binary Search | Easy | python, c, c++ | O(log(N)) | O(1) |
| 278 | First Bad Version | Binary Search, Interfactive | Easy | pythonc | O(log(N)) | O(1) |
| 35 | Search Instert Position | Array, Binary Search | Easy | python | O(log(N)) | O(1) |
| 977 | Squares of a Sorted Array | Array, Two Pointers, Sorting | Easy | python | O(N) | O(1) |
| 189 | Rotate Array | Array, Math, Two Pointers | Medium | c++, python | O(N) | O(N) |
| 167 | Two Sum II - Input Array Is Sorted | Array, Two Pointers, Binary Search | Medium | python | O(N) | O(1) |
| 344 | Reverse String | Two Pointers, String | Easy | python, c++ | O(N) | O(1) |
| 557 | Reverse Words in a String III | Two Pointers, String | Easy | python | O(N^2) | O(N) |
| 876 | Middle of the Linked List | Linked List, Two Pointers | Easy | c | O(N) | O(1) |
| 19 | Remove Nth Node From End of List | Linked List, Two Pointers | Medium | c, c++ | O(N) | O(1) |
| 3 | Longest Substring Without Repeating Characters | Hash Table, String, Sliding Window | Medium | c, c++ | O(N) | O(1) |
| 209 | Minimum Size Subarray Sum | Array, Binary Search, Sliding Window | Medium | c | O(N) | O(1) |
| 219 | Contains Duplicate II | Array, Hash Table, Sliding Window | Easy | c++ | O(N) | O(M) |
| 220 | Contains Duplicate III | Array, Sliding Window, Sorting, Bucket Sort, Ordered Set | Hard | c++ | O(N) | O(N) |
| 221 | Maximal Square | Array, Dynamic Programming, Matrix | Medium | c++ | O(N) | O(N) |
| 213 | House Robber II | Array, Dynamic Programming | Medium | c++ | O(N) | O(N) |
| 474 | Ones and Zeroes | Array, String, Dynamic Programming | Medium | c++ | O(N*M*L) | O(N*M) |
| 494 | Ones and Zeroes | Array, Dynamic Programming, Backtracking | Medium | c++ | O(N*T) | O(N*T) |
| 322 | Coin Change | Array, Dynamic Programming, DFS | Medium | c++ | O(N*M) | O(M) |
| 518 | Coin Change II | Array, Dynamic Programming | Medium | c++ | O(N*M) | O(M) |
| 62 | Unique Path | Array, Dynamic Programming, Combinatorics | Medium | c++ | O(N*M) | O(N*M) |
| 63 | Unique Path II | Array, Dynamic Programming | Medium | c++ | O(N*M) | O(N*M) |
| 46 | Permutations | Array, Backtracking | Medium | c++ | O(N*N!) | O(N) |
| 47 | Permutations II | Array, Backtracking | Medium | c++ | O(N*N!) | O(N) |
| 78 | Subsets | Array, Backtracking, Bit Manipulation | Medium | c++ | O(N*2^N^) | O(N) |
| 90 | Subsets II | Array, Backtracking, Bit Manipulation | Medium | c++ | O(N*2^N^) | O(N) |
| 33 | Serach in Rotated Sorted Array | Array, Binary Search | Medium | c++ | O(log(N)) | O(1) |
| 70 | Climbing Stairs | Math, Dynamic Programming, Memorization | Easy | c++ | O(N) | O(N) |
| 27 | Remove Elements | Array, Two Pointers | Easy | c++ | O(N) | O(1) |
| 1796 | Second Largest Digit in a String | Hash Table, String | Easy | c++ | O(N) | O(1) |
| 1540 | Can Convert String in K Moves | Hash Table, String | Easy | c++ | O(N) | O(1) |
| 2465 | Numbers of Distinct Averages | Array, Hash Table, Two Pointers, Sorting | Easy | c++ | O(N) | O(1) |
| 2006 | Count Number of Pairs With Absolute Difference K | Array, Hash Table | Easy | c++ | O(N) | O(N) |
| 100 | Same Tree | Tree, Depth-First Search, Breadth-First Search, Binary Tree | Easy | c++ | O(1) | O(1) |
| 101 | Symmetric Tree | Tree, Depth-First Search, Breadth-First Search, Binary Tree | Easy | c++ | O(log(N)) | O(1) |
| 104 | Maximum Depth of Binary Tree | Tree, Depth-First Search, Breadth-First Search, Binary Tree | Easy | c++ | O(N) | O(N) |
| 108 | Convert Sorted Array to Binary Search Tree | Array, Divide-And-Conquer, Tree ,Breadth-First Search, Binary Tree | Easy | c++ | O(N) | O(N) |
| 110 | Balanced Binary Tree | Array, Divide-And-Conquer, Tree ,Breadth-First Search, Binary Tree | Easy | c++ | O(N) | O(1) |
| 112 | Path Sum | Tree, Depth-First Search, Breadth-First Search, Binary Tree | Easy | c++ | O(N) | O(1) |
| 118 | Pascal's Triangle | Array, Dynamic Programming | Easy | c++ | O(N^2) | O(N^2) |
| 121 | Best Time to Buy and Sell Stock | Array, Dynamic Programming | Easy | c++ | O(N) | O(1) |
| 509 | Fibonacci Number | Dynamic Programming, Recursion, Memorization | Easy | c++ | O(N) | O(N) |
| 122 | Best Time to Buy and Sell Stock II | Array, Dynamic Programming | Medium | c++ | O(N) | O(1) |
| 125 | Valid Palindrome | Two Pointers, String | Easy | c++ | O(N) | O(1) |
| 141 | Linked List Cycle | Hash Table, Linked List, Two Pointers | Easy | c++ | O(N) | O(1) |
| 144 | Binary Tree Preorder Traversal | Stack, Tree, Detph-First Search, Binary Tree | Easy | c++ | O(N) | O(N) |
| 171 | Excel Sheet Column Number | Math, String | Easy | c++ | O(N) | O(1) |
| 168 | Excel Sheet Column Title | Math, String | Easy | c++ | O(N) | O(N) |
| 190 | Reverse Bits | Divide and Conquer, Bit Manipulation | Easy | c++ | O(1) | O(1) |
| 191 | Number of 1 Bits | Divide and Conquer, Bit Manipulation | Easy | c++ | O(1) | O(1) |
| 203 | Remove Linked List Elements | Linked List, Recursion | Easy | c++ | O(N) | O(1) |
| 912 | Sort an Array | Array, Divide and Conquer, Sorting, Heap (Priority Queue), Merge Sort, Bucket Sort, Radix Sort, Counting Sort | Easy | c++ | O(NLogN) | O(N) |
| 217 | Contains Duplicate | Array, Hash Table, Sorting | Easy | c++ | O(N) | O(N) |
| 222 | Count Complete Tree Nodes | Binary Search, Bit Manipulation, Tree, Binary Tree | Easy | c++ | O(N) | O(1) |
| 2215 | Find the Difference of Two Arrays | Array, Hash Tables | Easy | c++ | O(N) | O(N) |
| 1217 | Minimum Cost to Move Chips to The Same Position | Array, Math, Greedy | Easy | c++ | O(N) | O(1) |
| 2578 | Split With Minimum Sum | Math, Greedy, Sorting | Easy | c++ | O(1) | O(1) |
| 46 | Permutations | Array, Backtracking | Medium | c++ | O(N*N!) | O(N) |
| 118 | Pascal's Triangle | Array, Dynamic Programming | Easy | c++ | O(N^2) | O(N^2) |
| 48 | Rotate Image | Array, Math, Matrix | Medium | c++ | O(N*2) | O(1) |
| 136 | Single Number | Array, Bit Mainulation | Easy | c++ | O(N) | O(1) |
| 108 | Convert Sorted Array to Binary Search Tree | Array, Divide-And-Conquer, Tree ,Breadth-First Search, Binary Tree | Easy | c++ | O(N) | O(N) |
| 289 | Game of Life | Array, Matrix, Simulation | Easy | c++ | O(MN^2) | O(MN) |
| 49 | Group of Anagrams | Array, Hash Table, String, Sorting | Medium | c++ | O(NKLog(K)) | O(N) |
| 215 | Kth Largest Element in an Array | Array, Divide and Conquer, Sorting, Heap(Priority Queue), Quickselect | Easy | c++ | O(NlogK) | O(K) |
| 122 | Best Time to Buy and Sell Stock II | Array, Dynamic Programming, Greedy | Medium | c++ | O(N) | O(1) |
| 238 | Product of Array Except Self | Array, Prefix Sum | Medium | c++ | O(N) | O(1) |
| 268 | Missing Number | Array, Hash Table, Math, Binary Search, Bit Manipulation, Sorting | Easy | c++ | O(N) | O(1) |
| 169 | Majority Element | Array, Hash Table, Divide and Conquer, Sorting, Counting | Easy | c++ | O(N) | O(1) |
| 105 | Construct Binary Tree from Preorder and Inorder Traversal | Array, Hash Table, Divide and Conquer, Tree, Binary Tree | Medium | c++ | O(N) | O(N) |
| 347 | Top K Frequent Elements | Array, Hash Table, Divide and Conquer, Sorting, Heap (Priority Queue), Bucket Sort, Counting, Quickselect | Medium | c++ | O(NLogN) | O(N) |
| 378 | Kth Smallest Element in a Sorted Matrix | Array, Binary Search, Sorting, Heap (Priority Queue), Matrix | Medium | c++ | O(NNlogN) | O(1) |
| 75 | Sort Colors | Array, Two Pointers, Sorting | Medium | c++ | O(N+M) | O(M) |
| 287 | Find the Duplicated Number | Array, Two Pointers, Binary Search, Bit Manipulation | Medium | c++ | O(N) | O(1) |
| 200 | Number of Islands | Array, Depth-First Search, Breadth-First Search, Union Find, Matrix | Medium | c++ | O(N^2) | O(1) |
| 384 | Shuffle an Array | Array, Math, Ramdomized | Medium | c++ | O(N) | O(N) |
| 454 | 4Sum II | Array, Hash Table | Medium | c++ | O(N^2) | O(N^2) |
| 18 | 4Sum | Array, Two Pointers, Sorting | Medium | c++ | O(N^3) | O(1) |
| 300 | Longest Increasing Subsequence | Array, Binary Search, Dynamic Programming | Medium | c++ | O(N^2) | O(N) |
| 11 | Container With Most Water | Array, Two Pointers, Greedy | Medium | c++ | O(N) | O(1) |
| 73 | Set Matrix Zeroes | Array, Hash Table, Matrix | Medium | c++ | O(NM+V) | O(V) |
| 380 | Insert Delete GetRandom O(1) | Array, Hash Table, Math, Design, Randomized | Medium | c++ | O(1) | O(N) |
| 329 | Longest Increasing Path in a Matrix | Array, Dynamic Programming, Depth-First Search, Breadth-First Search, Graph, Topological Sort, Memoization, Matrix | Hard | c++ | O(NM) | O(NM) |
| 240 | Search a 2D Matrix II | Array, Binary Search, Divide and Conquer, Matrix | Medium | c++ | O(NLogM) | O(1) |
| 198 | House Robber | Array, Dynamic Programming | Medium | c++ | O(N) | O(1) |
| 150 | Evaluate Reverse Polish Notation | Array, Math, Stack | Medium | c++ | O(N) | O(N) |
| 88 | Merge Sorted Array | Array, Two Pointers, Sorting | Easy | c++ | O(N) | O(1) |
| 54 | Spiral Matrix | Array, Matrix, Simulation | Medium | c++ | O(NM) | O(NM) |
| 128 | Longest Consecutive Sequence | Array, Hash Table, Union Find | Medium | c++ | O(N^2) | O(N) |
| 140 | Word Break II | Array, Hash Table, String, Dynamic Programming, Memoization | Hard | c++ | O(NM) | O(N) |
| 56 | Merge Intervals | Array, Sorting | Medium | c++ | O(NLogN) | O(N) |
| 139 | Word Break | Array, Hash Table, String, Dynamic Programming, Trie, Memoization | Medium | c++ | O(NM) | O(N) |
| 239 | Sliding Window Maximum | Array, Queue, Sliding Window, Heap (Priority Queue), Monotonic Queue | Medium | c++ | O(N) | O(N) |
| 162 | Find Peak Element | Array, Binary Search | Medium | c++ | O(logN) | O(1) |
| 134 | Gas Station | Array, Greedy | Medium | c++ | O(N) | O(1) |
| 34 | Find First and Last Position of Element in Sorted Array | Array, Binary Search | Medium | c++ | O(logN) | O(1) |
| 79 | Word Search | Array, String, Backtracking, Matrix | Medium | c++ | O(NMK) | O(1) |
| 334 | Increasing Triplet Subsequence | Array, Greedy | Medium | c++ | O(N) | O(1) |
| 130 | Surrounded Regions | Array, Depth-First Search, Breadth-First Search, Union Find, Matrix | Medium | c++ | O(NM) | O(1) |
| 55 | Jump Game | Array, Dynamic Programming, Greedy | Medium | c++ | O(N) | O(N) |
| 179 | Largest Number | Array, String, Greedy, Sorting | Medium | c++ | O(NlogN) | O(N) |
| 152 | Maximum Product Subarray | Array, Dynamic Programming | Medium | c++ | O(N) | O(N) |
| 324 | Wiggle Sort II | Array, Divide and Conquer, Sorting, Quickselect | Medium | c++ | O(NlogN) | O(N) |
| 204 | Count Primes | Array, Math, Enumeration, Number Theory | Medium | c++ | O(NlogN) | O(N) |
| 149 | Max Points on a Line | Array, Hash Table, Math, Geometry | Hard | c++ | O(N^2) | O(N) |
| 208 | Implement Trie (Prefix Tree) | Hash Table, String, Design, Trie | Medium | c++ | O(N) | O(N) |
| 212 | Word Search II | Array, String, Backtracking, Trie, Matrix | Hard | c++ | O(NMK) | O(K) |
| 41 | Find Missing Postive | Array, Hash Table | Hard | c++ | O(N) | O(1) |
| 146 | LRU Cache | Hash Table, Linked List, Design, Doubly-Linked List | Medium | c++ | O(1) | O(N) |
| 91 | Decode Ways | String, Dynamic Programming | Medium | c++ | O(N) | O(N) |
| 5 | Longest Palindromic Substring | String, Dynamic Programming | Medium | c++ | O(N^2) | O(N) |
| 22 | Generate Parentheses | String, Dynamic Programming, Backtracking | Medium | c++ | O(2^N) | O(N) |
| 2824 | Count Pairs Whose Sum is Less than Target | Array, Two Pointers, Binary Search, Sorting | Easy | c++ | O(NlogN) | O(1) |
| 475 | Heaters | Array, Two Pointers, Binary Search, Sorting | Medium | c++ | O(NlogM) | O(1) |
| 1343 | Number of Sub-arrays of Size K and Average Greater than or Equal to Threshold | Array, Sliding Window | Medium | c++ | O(N) | O(1) |
| 1347 | Minimum Number of Steps to Make Two Strings Anagram | Hash Table, String, Counting | Medium | c++ | O(N) | O(1) |
| 894 | All Possible Full Binary Trees | Dynamic Programming, Tree, Recursion, Memoization, Binary Tree | Medium | c++ | O(N) | O(N) |
| 1641 | Count Sorted Vowel Strings | Math, Dynamic Programming, Combinatorics | Medium | c++ | O(N) | O(1) |
| 242 | Valid Anagram | Hash Table, String, Sorting | Easy | c++ | O(N) | O(N) |
| 36 | Valid Sudoku | Array, Hash Table, Matrix | Medium | c++ | O(1) | O(1) |
| 20 | Valid Parentheses | String, Stack | Easy | c++ | O(N) | O(N) |
| 155 | Min Stack | Stack, Design | Medium | c++ | O(1) | O(N) |
| 739 | Daily Temperatures | Array, Stack, Monotonic Stack | Medium | c++ | O(N) | O(N) |
| 853 | Car Fleet | Array, Stack, Sorting, Monotonic Stack | Medium | c++ | O(NlogN) | O(N) |
| 496 | Next Greater Element I | Array, Hash Table, Stack, Monotonic Stack | Medium | c++ | O(N+M) | O(M) |
| 907 | Sum of Subarray Minimums | Array, Dynamic Programming, Stack, Monotonic Stack | Medium | c++ | O(N) | O(N) |
| 84 | Largest Rectangle in Histogram | Array, Stack, Monotonic Stack | Hard | c++ | O(N) | O(N) |
| 167 | Two Sum II - Input Array Is Sorted | Array, Two Pointers, Binary Search | Medium | c++ | O(N) | O(1) |
| 42 | Trapping Rain Water | Array, Two Pointers, Dynamic Programming, Stack, Monotonic Stack | Hard | c++ | O(N) | O(N) |
| 74 | Search a 2D Matrix | Array, Binary Search, Matrix | Medium | c++ | O(log(N*M)) | O(1) |
| 874 | Koko Eating Bananas | Array, Binary Search | Medium | c++ | O(Nlog(V)) | O(1) |
| 981 | Time Based Key-Value Store | Hash Table, String, Binary Search, Design | Medium | c++ | O(log(N)) | O(N) |
| 4 | Median of Two Sorted Arrays | Array, Binary Search, Divide and Conquer | Hard | c++ | O(log(NM)) | O(1) |
| 1588 | Sum of All Odd Length Subarrays | Array, Math, Prefix Sum | Easy | c++ | O(N) | O(1) |
| 2384 | Largest Palindromic Number | Hash Table, String, Greedy | Medium | c++ | O(N) | O(N) |
| 464 | Can I Win | Math, Dynamic Programming, Bit Manipulation, Memoization, Game Theory, Bitmask | Medium | c++ | O(2^N) | O(10^N) |
| 424 | Longest Repeating Character Replacement | Hash Table, String, Sliding Window | Medium | c++ | O(N) | O(1) |
| 567 | Permutation in String | Hash Table, Two Pointers, String, Sliding Window | Medium | c++ | O(N) | O(1) |
| 76 | Minimum Window Substring | Hash Table, String, Sliding Window | Hard | c++ | O(N) | O(1) |
| 21 | Merge Two Sorted Lists | Linked List, Recursion | Easy | c++ | O(N) | O(1) |
| 143 | Reorder List | Linked List, Two Pointers, Stack, Recursion | Medium | c++ | O(N) | O(N) |
| 138 | Copy List with Random Pointer | Hash Table, Linked List | Medium | c++ | O(N) | O(N) |
| 142 | Linked List Cycle II | Hash Table, Linked List, Two Pointers | Medium | c++ | O(N) | O(1) |
| 23 | Merge k Sorted Lists | Linked List, Divide and Conquer, Heap (Priority Queue), Merge Sort | Hard | c++ | O(NlogK) | O(K) |
| 25 | Reverse Nodes in k-Group | Linked List, Recursion | Hard | c++ | O(N) | O(1) |
| 763 | Partition Labels | Hash Table, Two Pointers, String, Greedy | Medium | c++ | O(N) | O(N) |
| 226 | Invert Binary Tree | Tree, Depth-First Search, Breadth-First Search, Binary Tree | Easy | c++ | O(N) | O(1) |
| 543 | Diameter of Binary Tree | Tree, Depth-First Search, Binary Tree | Easy | c++ | O(N) | O(1) |
| 572 | Subtree of Another Tree | Tree, Depth-First Search, String Matching, Binary Tree, Hash Function | Easy | c++ | O(N) | O(1) |
| 102 | Binary Tree Level Order Traversal | Tree, Breadth-First Search, Binary Tree | Medium | c++ | O(N) | O(2^D) |
| 235 | Lowest Common Ancestor of a Binary Search Tree | Tree, Depth-First Search, Binary Search Tree, Binary Tree | Medium | c++ | O(N) | O(1) |
| 199 | Binary Tree Right Side View | Tree, Depth-First Search, Breadth-First Search, Binary Tree | Medium | c++ | O(N) | O(logN) |
| 1448 | Count Good Nodes in Binary Tree | Tree, Depth-First Search, Breadth-First Search, Binary Tree | Medium | c++ | O(N) | O(1) |
| 98 | Validate Binary Search Tree | Tree, Depth-First Search, Breadth-First Search, Binary Tree | Medium | c++ | O(N) | O(1) |
| 1535 | Find the Winner of an Array Game | Array, Simulation | Medium | c++ | O(N) | O(N) |
| 230 | Kth Smallest Element in a BST | Tree, Depth-First Search, Binary Search Tree, Binary Tree | Medium | c++ | O(K) | O(1) |
| 124 | Binary Tree Maximum Path Sum | Dynamic Programming, Tree, Depth-First Search, Binary Tree | Hard | c++ | O(N) | O(1) |
| 297 | Serialize and Deserialize Binary Tree | String, Tree, Depth-First Search, Breadth-First Search, Design, Binary Tree | Hard | c++ | O(N) | O(N) |
| 211 | Design Add and Search Words Data Structure | String, Depth-First Search, Design, Trie | Medium | c++ | O(N) | O(N) |
| 703 | Kth Largest Element in a Stream | Tree, Design, Binary Search Tree, Heap (Priority Queue), Binary Tree, Data Stream | Easy | c++ | O(N) | O(K) |
| 1046 | Last Stone Weight | Array, Heap (Priority Queue) | Easy | c++ | O(NlogN) | O(N) |
| 973 | K Closest Points to Origin | Array, Math, Divide and Conquer, Geometry, Sorting, Heap (Priority Queue), Quickselect | Medium | c++ | O(NlogK) | O(K) |
| 621 | Task Scheduler | Array, Hash Table, Greedy, Sorting, Heap (Priority Queue), Counting | Medium | c++ | O(N) | O(N) |
| 355 | Design Twitter | Hash Table, Linked List, Design, Heap (Priority Queue) | Medium | c++ | O(K*NlogN) | O(N) |
| 904 | Fruit Into Baskets | Array, Hash Table, Sliding Window | Medium | c++ | O(N) | O(1) |
| 295 | Find Median from Data Stream | Two Pointers, Design, Sorting, Heap (Priority Queue), Data Stream | Hard | c++ | O(logN) | O(N) |
| 39 | Combination Sum | Array, Backtracking | Medium | c++ | O(NlogN+K/min) | O(K/min) |
| 40 | Combination Sum II | Array, Backtracking | Medium | c++ | O(NlogN+M*2^N) | O(N) |
| 131 | Palindrome Partitioning | String, Dynamic Programming, Backtracking | Medium | c++ | O(N^2) | O(N^2) |
| 17 | Letter Combinations of a Phone Number | Hash Table, String, Backtracking | Medium | c++ | O(N) | O(N) |
| 746 | Min Cost Climbing Stairs | Array, Dynamic Programming | Easy | c++ | O(N) | O(N) |
| 51 | N-Queens | Array, Backtracking | Hard | c++ | O(N!) | O(N) |
| 3112 | Minimum Time to Visit Disappearing Nodes | Graph | Medium | c++ | O(N^V) | O(N) |
| 3110 | Score of a String | String | Easy | c++ | O(N) | O(1) |
| 3111 | Minimum Rectangles to Cover Points | Array | Medium | c++ | O(NlogN) | O(N) |
| 647 | Palindromic Substrings | Two Pointers, String, Dynamic Programming | Medium | c++ | O(N^2) | O(1) |
| 416 | Partition Equal Subset Sum | Array, Dynamic Programming | Medium | c++ | O(N^2) | O(N) |
| 695 | Max Area of Island | Array, Depth-First Search, Breadth-First Search, Union Find, Matrix | Medium | c++ | O(NMK) | O(1) |
| 133 | Clone Graph | Hash Table, Depth-First Search, Breadth-First Search, Graph | Medium | c++ | O(NV) | O(N) |
| 994 | Rotting Oranges | Array, Breadth-First Search, Matrix | Medium | c++ | O(NM) | O(NM) |
| 417 | Pacific Atlantic Water Flow | Array, Depth-First Search, Breadth-First Search, Matrix | Medium | c++ | O(NM) | O(NM) |
| 207 | Course Schedule | Depth-First Search, Breadth-First Search, Graph, Topological Sort | Medium | c++ | O(N+E) | O(N) |
| 1391 | Check if There is a Valid Path in a Grid | Array, Depth-First Search, Breadth-First Search, Union Find, Matrix | Medium | c++ | O(N*M) | O(1) |
| 2830 | Maximize the Profit as the Salesman | Array, Hash Table, Binary Search, Dynamic Programming, Sorting | Medium | c++ | O(MlogM) | O(M) |
| 210 | Course Schedule II | Depth-First, Search, Breadth-First Search, Graph, Topological Sort | Medium | c++ | O(N+E) | O(N*E) |
| 684 | Redundant Connection | Depth-First Search, Breadth-First Search, Union Find, Graph | Medium | c++ | O(N) | O(N) |
| 127 | Word Ladder | Hash Table, String, Breadth-First Search | Hard | c++ | O(WNlogN) | O(N) |
| 1143 | Longest Common Subsequence | String, Dynamic Programming | Medium | c++ | O(NM) | O(NM) |
| 435 | Non-overlapping Intervals | Array, Dynamic Programming, Greedy, Sorting | Medium | c++ | O(NlogN) | O(1) |
| 57 | Insert Interval | Array | Medium | c++ | O(N) | O(N) |
| 309 | Best Time to Buy and Sell Stock with Cooldown | Array, Dynamic Programming | Medium | c++ | O(N) | O(N) |
| 97 | Interleaving String | String, Dynamic Programming | Medium | c++ | O(N*M) | O(N*M) |
| 115 | Distinct Subsequences | String, Dynamic Programming | Hard | c++ | O(N*M) | O(N*M) |
| 72 | Edit Distance | String, Dynamic Programming | Hard | c++ | O(N*M) | O(N*M) |
| 1705 | Maximum Number of Eaten Apples | Array, Greedy, Heap (Priority Queue) | Medium | c++ | O(NlogN) | O(N) |
| 1367 | Linked List in Binary Tree | Linked List, Tree, Depth-First Search, Breadth-First Search, Binary Tree | Medium | c++ | O(N+M) | O(1) |
| 312 | Burst Balloons | Array, Dynamic Programming | Hard | c++ | O(N^2) | O(N^2) |
| 1851 | Minimum Interval to Include Each Query | Array, Binary Search, Line Sweep, Sorting, Heap (Priority Queue) | Hard | c++ | O((N+M)logN) | O(N+M) |
| 338 | Counting Bits | Dynamic Programming | ||||
| Bit Manipulation | Easy | c++ | O(N) | O(N) | ||
| 371 | Sum of Two Integers | Math, Bit Manipulation | Medium | c++ | O(1) | O(1) |
| 7 | Reverse Integer | Math | Medium | c++ | O(N) | O(1) |
| 252 | Meeting Rooms | Intervals | Easy | c++ | O(N) | O(1) |
| 253 | Meeting Rooms II | Intervals | Easy | c++ | O(N^2) | O(N) |
| 53 | Maximum Subarray | Array, Divide and Conquer, Dynamic Programming | Medium | c++ | O(N) | O(1) |
| 45 | Jump Game II | Array, Dynamic Programming, Greedy | Medium | c++ | O(N) | O(1) |
| 846 | Hand of Straights | Array, Hash Table, Greedy, Sorting | Medium | c++ | O(NlogN) | O(N) |
| 1899 | Merge Triplets to Form Target Triplet | Array, Greedy | Medium | c++ | O(N) | O(N) |
| 678 | Valid Parenthesis String | String, Dynamic Programming, Stack, Greedy | Medium | c++ | O(N) | O(1) |
| 1509 | Minimum Difference Between Largest and Smallest Value in Three Moves | Array, Greedy, Sorting | Medium | c++ | O(1) | O(1) |
| 1525 | Number of Good Ways to Split a String | Hash Table, String, Dynamic Programming, Bit Manipulation | Medium | c++ | O(N) | O(N) |
| 3114 | Latest Time You Can Obtain After Replacing Characters | String, Enumeration | Easy | c++ | O(1) | O(1) |
| 1200 | Minimum Absolute Difference | Array, Sorting | Easy | c++ | O(NlogN) | O(N) |
| 1007 | Minimum Domino Rotations For Equal Row | Array, Greedy | Medium | c++ | O(N) | O(1) |
| 1888 | Minimum Number of Flips to Make the Binary String Alternating | String, Dynamic Programming, Greedy, Sliding Window | Medium | c++ | O(N) | O(1) |
| 274 | H-Index | Array, Sorting, Counting Sort | Medium | c++ | O(N) | O(1) |
| 1584 | Min Cost to Connect All Points | Array, Union Find, Graph, Minimum Spanning Tree | Medium | c++ | O(N^2) | O(N) |
| 743 | Network Delay Time | Depth-First Search, Breadth-First Search, Graph, Heap (Priority Queue), Shortest Path | Medium | c++ | O(N^2) | O(N^2) |
| 1825 | Finding MK Average | Design, Queue, Heap (Priority Queue), Data Stream, Ordered Set | Hard | c++ | O(logN) | O(1) |
| 874 | Walking Robot Simulation | Array, Hash Table, Simulation | Medium | c++ | O(N) | O(N) |
| 2547 | Minimum Cost to Split an Array | Array, Hash Table, Dynamic Programming, Counting | Hard | c++ | O(N^2) | O(N) |
| 2982 | Find Longest Special Substring That Occurs Thrice II | Hash Table, String, Binary Search, Sliding Window, Counting | Medium | c++ | O(N) | O(N) |
| 2958 | Length of Longest Subarray With at Most K Frequency | Array, Hash Table, Sliding Window | Medium | c++ | O(N) | O(N) |
| 359 | Logger Rate Limiter | Hash Table, Design, Data Stream | Easy | c++ | O(1) | O(N) |
| 2402 | Meeting Rooms III | Array, Hash Table, Sorting, Heap (Priority Queue), Simulation | Hard | c++ | O(NlogN) | O(N) |
| 1110 | Delete Nodes And Return Forest | Array, Hash Table, Tree, Depth-First Search, Binary Tree | Medium | c++ | O(V) | O(V) |
| 715 | Range Module | Design, Segment Tree, Ordered Set | Hard | c++ | O(NlogN) | O(NlogN) |
| 939 | Minimum Area Rectangle | Array, Hash Table, Math, Geometry, Sorting | Medium | c++ | O(N^2) | O(1) |
| 1101 | The Earliest Moment When Everyone Become Friends | Array, Union Find, Sorting | Medium | c++ | O(N^2) | O(N) |
| 975 | Odd Even Jump | Array, Dynamic Programming, Stack, Monotonic Stack, Ordered Set | Hard | c++ | O(NlogN) | O(N) |
| 2863 | Maximum Length of Semi-Decreasing Subarrays | Array, Hash Table, Sorting | Medium | c++ | O(N) | O(N) |
| 2013 | Detect Squares | Array, Hash Table, Design, Counting | Medium | c++ | O(N) | O(N) |
| 2458 | Height of Binary Tree After Subtree Removal Queries | Array, Tree, Depth-First Search, Breadth-First Search, Binary Tree | Hard | c++ | O(V+N) | O(V) |
| 85 | Maximal Rectangle | Array, Dynamic Programming, Stack, Matrix, Monotonic Stack | Hard | c++ | O(N*M) | O(N) |
| 554 | Brick Wall | Array, Hash Table | Medium | c++ | O(N*M) | O(N) |
| 2184 | Number of Ways to Build Sturdy Brick Wall | Array, Dynamic Programming, Bit Manipulation, Bitmask | Medium | c++ | O(2W*H) | O(H*2W) |
| 963 | Minimum Area Rectangle II | Array, Math, Geometry | Medium | c++ | O(N^2) | O(N^2) |
| 2290 | Minimum Obstacle Removal to Reach Corner | Array, Breadth-First Search, Graph, Heap (Priority Queue), Matrix, Shortest Path | Hard | c++ | O(N^2) | O(N^2) |
| 655 | Print Binary Tree | Tree, Depth-First Search, Breadth-First Search, Binary Tree | Medium | c++ | O(V) | O(V) |
| 2316 | Count Unreachable Pairs of Nodes in an Undirected Graph | Depth-First Search, Breadth-First, Search, Union Find, Graph | Medium | c++ | O(N^2) | O(N) |
| 778 | Swim in Rising Water | Array, Binary Search, Depth-First Search, Breadth-First Search, Union Find, Heap (Priority Queue), Matrix | Hard | c++ | O(N^2) | O(N^2) |
| 1136 | Parallel Courses | Graph, Topological Sort | Medium | c++ | O(V+E) | O(V+E) |
| 2115 | Find All Possible Recipes from Given Supplies | Array, Hash Table, String, Graph, Topological Sort | Medium | c++ | O(NM+K) | O(NM+K) |
| 833 | Find And Replace in String | Array, String, Sorting | Medium | c++ | O(N+M) | O(M+K) |
| 269 | Alien Dictionary | Array, String, Depth-First Search, Breadth-First Search, Graph, Topological Sort | Hard | c++ | O(NW+E) | O(N+E) |
| 2122 | Recover the Original Array | Array, Hash Table, Sorting, Enumeration | Hard | c++ | O(N^2) | O(N) |
| 2973 | Find Number of Coins to Place in Tree Nodes | Dynamic Programming, Tree, Depth-First Search, Sorting, Heap (Priority Queue) | Medium | c++ | O(E) | O(N+E) |
| 365 | Water and Jug Problem | Dynamic Programming, Tree, Depth-First Search, Sorting, Heap (Priority Queue) | Medium | c++ | O(E) | O(N+E) |
| 1820 | Maximum Number of Accepted Invitations | Array, Backtracking, Matrix | Medium | c++ | O(N*M) | O(N) |
| 1756 | Design Most Recently Used Queue | Array, Hash Table, Stack, Design, Binary Indexed Tree, Ordered Set | Medium | c++ | O(N) | O(N) |
| 1940 | Longest Common Subsequence Between Sorted Arrays | Array, Hash Table, Counting | Medium | c++ | O(MNlogM) | O(N) |
| 2486 | Append Characters to String to Make Subsequence | Two Pointers, String, Greedy | Medium | c++ | O(N) | O(1) |
| 1005 | Maximize Sum Of Array After K Negations | Array, Greedy, Sorting | Easy | c++ | O(NlogN) | O(1) |
| 409 | Longest Palindrome | Hash Table, String, Greedy | Easy | c++ | O(N) | O(N) |
| 1605 | Find Valid Matrix Given Row and Column Sums | Array, Greedy, Matrix | Medium | c++ | O(NM) | O(NM) |
| 787 | Cheapest Flights Within K Stops | Dynamic Programming, Depth-First Search, Breadth-First Search, Graph, Heap (Priority Queue), Shortest Path | Medium | c++ | O(N^2*K) | O(N^2) |
| 2191 | Sort the Jumbled Numbers | Array, Sorting | Medium | c++ | O(N*(logN + W)) | O(N) |
| 1636 | Sort Array by Increasing Frequency | Array, Hash Table, Sorting | Easy | c++ | O(NlogN) | O(N) |
| 1137 | N-th Tribonacci Number | Math, Dynamic Programming, Memoization | Easy | c++ | O(N) | O(N) |
| 740 | Delete and Earn | Array, Hash Table, Dynamic Programming | Medium | c++ | O(NlogN) | O(N) |
| 1929 | Concatenation of Array | Array, Simulation | Easy | c++ | O(N) | O(N) |
| 1299 | Replace Elements with Greatest Element on Right Side | Array | Easy | c++ | O(N) | O(1) |
| 58 | Length of Last Word | String | Easy | c++ | O(N) | O(1) |
| 929 | Unique Email Address | Array, Hash Table, String | Easy | c++ | O(N) | O(N) |
| 609 | Can Place Flowers | Array, Greedy | Easy | c++ | O(N) | O(1) |
| 303 | Range Sum Query - Immutable | Array, Design, Prefix Sum | Easy | c++ | O(N) | O(1) |
| 1189 | Maximum Number of Balloons | Hash Table, String, Counting | Easy | c++ | O(N) | O(1) |
| 290 | Word Pattern | Hash Table, String | Easy | c++ | O(N+M) | O(N+M) |
| 706 | Design HashMap | Array, Hash Table, Linked List, Design, Hash Function | Easy | c++ | O(1) | O(N) |
| 705 | Design HashSet | Array, Hash Table, Linked List, Design, Hash Function | Easy | c++ | O(1) | O(N) |
| 896 | Monotonic Array | Array | Easy | c++ | O(N) | O(1) |
| 1512 | Number of Good Pairs | Array, Hash Table, Math, Counting | Easy | c++ | O(N) | O(N) |
| 119 | Pascal's Triangle II | Array, Dynamic Programming | Easy | c++ | O(N^2) | O(N) |
| 2264 | Largest 3-Same-Digit Number in String | String | Easy | c++ | O(N) | O(N) |
| 1436 | Destination City | Array, Hash Table, String | Easy | c++ | O(N) | O(N) |
| 1913 | Maximum Product Difference Between Two Pairs | Array, Sorting | Easy | c++ | O(N) | O(1) |
| 1422 | Maximum Score After Splitting a String | String, Prefix Sum | Easy | c++ | O(N) | O(1) |
| 1496 | Path Crossing | Hash Table, String | Easy | c++ | O(N) | O(N) |
| 1758 | Minimum Changes To Make Alternating Binary String | String | Easy | c++ | O(N) | O(1) |
| 1897 | Redistribute Characters to Make All Strings Equal | Hash Table, String, Counting | Easy | c++ | O(W*N) | O(1) |
| 1624 | Largest Substring Between Two Equal Characters | Hash Table, String | Easy | c++ | O(N) | O(1) |
| 1700 | Number of Students Unable to Eat Lunch | Array, Stack, Queue, Simulation | Easy | c++ | O(N) | O(1) |
| 349 | Intersection of Two Arrays | Array, Hash Table, Two Pointers, Binary Search, Sorting | Easy | c++ | O(NlogN+MlogM) | O(K) |
| 387 | First Unique Character in a String | Hash Table, String, Queue, Counting | Easy | c++ | O(N) | O(1) |
| 387 | First Unique Character in a String | Hash Table, String, Queue, Counting | Easy | c++ | O(N) | O(1) |
| 645 | Set Mismatch | Array, Hash Table, Bit Manipulation, Sorting | Easy | c++ | O(N) | O(N) |
| 2073 | Time Needed to Buy Tickets | Array, Queue, Simulation | Easy | c++ | O(N) | O(1) |
| 1608 | Special Array With X Elements Greater Than or Equal X | Array, Binary Search, Sorting | Easy | c++ | O(NlogN) | O(1) |
| 535 | Encode and Decode TinyURL | Hash Table, String, Design, Hash Function | Medium | c++ | O(N) | O(N) |
| 560 | Subarray Sum Equals K | Array, Hash Table, Prefix Sum | Medium | c++ | O(N) | O(N) |
| 1930 | Unique Length-3 Palindromic Subsequences | Hash Table, String, Bit Manipulation, Prefix Sum | Medium | c++ | O(N^2) | O(N) |
| 1963 | Minimum Number of Swaps to Make the String Balanced | Two Pointers, String, Stack, Greedy | Medium | c++ | O(N) | O(1) |
| 2001 | Number of Pairs of Interchangeable Rectangles | Array, Hash Table, Math, Counting, Number Theory | Medium | c++ | O(N) | O(N) |
| 2002 | Maximum Product of the Length of Two Palindromic Subsequences | String, Dynamic Programming, Backtracking, Bit Manipulation, Bitmask | Medium | c++ | O(N^2) | O(N) |
| 2017 | Grid Game | Array, Matrix, Prefix Sum | Medium | c++ | O(N) | O(N) |
| 438 | Find All Anagrams in a String | Hash Table, String, Sliding Window | Medium | c++ | O(N+M) | O(1) |
| 28 | Find the Index of the First Occurrence in a String | Two Pointers, String, String Matching | Easy | c++ | O(NM) | O(1) |
| 523 | Continuous Subarray Sum | Array, Hash Table, Math, Prefix Sum | Medium | c++ | O(N) | O(N) |
| 838 | Push Dominoes | Two Pointers, String, Dynamic Programming | Medium | c++ | O(N) | O(N) |
| 187 | Repeated DNA Sequences | Hash Table, String, Bit Manipulation, Sliding Window, Rolling Hash, Hash Function | Medium | c++ | O(N) | O(N) |
| 1461 | Check If a String Contains All Binary Codes of Size K | Hash Table, String, Bit Manipulation, Rolling Hash, Hash Function | Medium | c++ | O(N) | O(N) |
| 304 | Range Sum Query 2D - Immutable | Array, Design, Matrix, Prefix Sum | Medium | c++ | O(1) | O(N*M) |
| 665 | Non-decreasing Array | Array | Medium | c++ | O(N) | O(1) |
| 1822 | Sign of the Product of an Array | Array, Math | Easy | c++ | O(N) | O(1) |
| 126 | Word Ladder II | Hash Table, String, Backtracking, Breadth-First Search | Hard | c++ | O(N*K) | O(N) |
| 1603 | Design Parking System | Design, Simulation, Counting | Easy | c++ | O(1) | O(1) |
| 2348 | Number of Zero-Filled Subarrays | Array, Math | Medium | c++ | O(N) | O(1) |
| 933 | Number of Recent Calls | Design, Queue, Data Stream | Easy | c++ | O(1) | O(1) |
| 362 | Design Hit Counter | Array, Binary Search, Design, Queue, Data Stream | Medium | c++ | O(N) | O(1) |
| 649 | Dota2 Senate | String, Greedy, Queue | Medium | c++ | O(N) | O(N) |
| 1396 | Design Underground System | Hash Table, String, Design | Medium | c++ | O(1) | O(N) |
| 1768 | Merge Strings Alternately | Two Pointers, String | Easy | c++ | O(N) | O(N) |
| 2483 | Minimum Penalty for a Shop | String, Prefix Sum | Medium | c++ | O(N) | O(1) |
| 799 | Champagne Tower | Dynamic Programming | Medium | c++ | O(N^2) | O(N^2) |
| 815 | Bus Routes | Array, Hash Table, Breadth-First Search | Hard | c++ | O(N*M) | O(N*M+S) |
| 754 | Reach a Number | Math, Binary Search | Medium | c++ | O(N) | O(1) |
| 280 | Wiggle Sort | Array, Greedy, Sorting | Medium | c++ | O(N) | O(1) |
| 271 | Encode and Decode Strings | Array, String, Design | Medium | c++ | O(N*W) | O(N*W) |
| 229 | Majority Element II | Array, Hash Table, Sorting, Counting | Medium | c++ | O(N) | O(1) |
| 2560 | House Robber IV | Array, Binary Search | Medium | c++ | O(N*logW) | O(1) |
| 1685 | Sum of Absolute Differences in a Sorted Array | Array, Math, Prefix Sum | Medium | c++ | O(N) | O(N) |
| 2353 | Design a Food Rating System | Hash Table, Design, Heap (Priority Queue), Ordered Set | Medium | c++ | O(NlogN) | O(N) |
| 2610 | Convert an Array Into a 2D Array With Conditions | Array, Hash Table | Medium | c++ | O(N) | O(N) |
| 2870 | Minimum Number of Operations to Make Array Empty | Array, Hash Table, Greedy, Counting | Medium | c++ | O(N) | O(N) |
| 1291 | Sequential Digits | Enumeration | Medium | c++ | O(DlogD) | O(D) |
| 2966 | Divide Array Into Arrays With Max Difference | Array, Greedy, Sorting | Medium | c++ | O(NlogN) | O(N) |
| 451 | Sort Characters By Frequency | Hash Table, String, Sorting, Heap (Priority Queue), Bucket Sort, Counting | Medium | c++ | O(NlogN) | O(N) |
| 2971 | Find Polygon With the Largest Perimeter | Array, Greedy, Sorting, Prefix Sum | Medium | c++ | O(NlogN) | O(1) |
| 1249 | Minimum Remove to Make Valid Parentheses | Stack, String, Array | Medium | c++ | O(N) | O(N) |
| 525 | Contiguous Array | Array, Prefix Sum, Hash Table | Medium | c++ | O(N) | O(N) |
| 2594 | Minimum Time to Repair Cars | Array, Binary Search | Medium | c++ | O(NlogK) | O(1) |
| 2055 | Plates Between Candles | Array, String, Binary Search, Prefix Sum | Medium | c++ | O(N+M) | O(N) |
| 491 | Non-decreasing Subsequences | Array, Hash Table, Backtracking, Bit Manipulation | Medium | c++ | O(N*2^N) | O(N*2^N) |
| 2826 | Sorting Three Groups | Array, Binary Search, Dynamic Programming | Medium | c++ | O(N) | O(1) |
| 68 | Text Justification | Array, String, Simulation | Hard | c++ | O(N*W) | O(N) |
| 680 | Valid Palindrome II | Two Pointers, String, Greedy | Easy | c++ | O(N) | O(1) |
| 2306 | Naming a Company | Array, Hash Table, String, Bit Manipulation, Enumeration | Hard | c++ | O(N) | O(N) |
| 1074 | Number of Submatrices That Sum to Target | Array, Hash Table, Matrix, Prefix Sum | Hard | c++ | O(N*M^2) | O(N) |
| 299 | Bulls and Cows | Hash Table, String, Counting | Medium | c++ | O(N) | O(1) |
| 1984 | Minimum Difference Between Highest and Lowest of K Scores | Array, Sliding Window, Sorting | Easy | c++ | O(NlogN) | O(1) |
| 2108 | Find First Palindromic String in the Array | Array, Two Pointers, String | Easy | c++ | O(N*M) | O(1) |
| 905 | Sort Array By Parity | Array, Two Pointers, Sorting | Easy | c++ | O(N) | O(1) |
| 557 | Reverse Words in a String III | Two Pointers, String | Easy | c++ | O(N) | O(1) |
| 844 | Backspace String Compare | Two Pointers, String, Stack, Simulation | Easy | c++ | O(N) | O(1) |
| 1662 | Check If Two String Arrays are Equivalent | Array, String | Easy | c++ | O(N) | O(1) |
| 80 | Remove Duplicates from Sorted Array II | Array, Two Pointers | Medium | c++ | O(N) | O(1) |
| 1498 | Number of Subsequences That Satisfy the Given Sum Condition | Array, Two Pointers, Binary Search, Sorting | Medium | c++ | O(N) | O(N) |
| 2678 | Number of Senior Citizens | Array, String | Easy | c++ | O(N) | O(1) |
| 916 | Word Subsets | Array, Hash Table, String | Medium | c++ | O(N*W1+M*L2) | O(1) |
| 1002 | Find Common Characters | Array, Hash Table, String | Easy | c++ | O(N*W) | O(1) |
| 2490 | Circular Sentence | String | Easy | c++ | O(N) | O(1) |
| 2559 | Count Vowel Strings in Ranges | Array, String, Prefix Sum | Medium | c++ | O(N+M) | O(N+M) |
| 1701 | Average Waiting Time | Array, Simulation | Medium | c++ | O(N) | O(1) |
| 2418 | Sort the People | Array, Hash Table, String, Sorting | Easy | c++ | O(NlogN) | O(N) |
| 791 | Custom Sort String | Hash Table, String, Sorting | Medium | c++ | O(NlogN) | O(N) |
| 1408 | String Matching in an Array | Array, String, String Matching | Easy | c++ | O(N^2*W) | O(N) |
| 485 | Max Consecutive Ones | Array | Easy | c++ | O(N) | O(1) |
| 2364 | Count Number of Bad Pairs | Array, Hash Table, Math, Counting | Medium | c++ | O(N) | O(N) |
| 884 | Uncommon Words from Two Sentences | Hash Table, String, Counting | Easy | c++ | O(N) | O(N) |
| 2381 | Shifting Letters II | Array, String, Prefix Sum | Medium | c++ | O(N) | O(N) |
| 2270 | Number of Ways to Split Array | Array, Prefix Sum | Medium | c++ | O(N) | O(N) |
| 1152 | Analyze User Website Visit Pattern | Array, Hash Table, String, Sorting | Medium | c++ | O(N log N + N * W^3$) | O(N) |
| 1769 | Minimum Number of Operations to Move All Balls to Each Box | Array, String, Prefix Sum | Medium | c++ | O(N) | O(N) |
| 383 | Ransom Note | Hash Table, String | Easy | c++ | O(N) | O(1) |
| 1684 | Count the Number of Consistent Strings | Array, Hash Table, String, Bit Manipulation, Counting | Easy | c++ | O(N) | O(1) |
| 3043 | Find the Length of the Longest Common Prefix | Array, Hash Table, String, Trie | Medium | c++ | O(N*D+M*D) | O(D*N) |
| 2257 | Count Unguarded Cells in the Grid | Array, Matrix, Simulation | Medium | c++ | O(N*M) | O(N*M) |