All Problems
516 problems · search by name, LC#, or tag · filter by difficulty & category
516 matches
| # | Title | Difficulty | Category | Tags |
|---|---|---|---|---|
| 1 | Two Sum↗ | Easy | Arrays | arrayhash-table |
| 2 | Add Two Numbers↗ | Medium | Linked List | linked-listmathrecursion |
| 3 | Longest Substring Without Repeating Characters↗ | Medium | Strings | hash-tablestringsliding-window |
| 4 | Median of Two Sorted Arrays↗ | Hard | Sorting | arraybinary-searchdivide-and-conquer |
| 5 | Longest Palindromic Substring↗ | Medium | Strings | two-pointersstringdynamic-programming |
| 6 | Zigzag Conversion↗ | Medium | Strings | string |
| 7 | Reverse Integer↗ | Medium | Math | math |
| 8 | String to Integer (atoi)↗ | Medium | Strings | string |
| 9 | Palindrome Number↗ | Easy | Strings | math |
| 10 | Regular Expression Matching↗ | Hard | Dynamic Programming | stringdynamic-programmingrecursion |
| 11 | Container With Most Water↗ | Medium | Arrays | arraytwo-pointersgreedy |
| 12 | Integer to Roman↗ | Medium | Math | hash-tablemathstring |
| 13 | Roman to Integer↗ | Easy | Math | hash-tablemathstring |
| 14 | Longest Common Prefix↗ | Easy | Strings | arraystringtrie |
| 15 | 3Sum↗ | Medium | Arrays | arraytwo-pointerssorting |
| 16 | 3Sum Closest↗ | Medium | Arrays | arraytwo-pointerssorting |
| 17 | Letter Combinations of a Phone Number↗ | Medium | Backtracking | hash-tablestringbacktracking |
| 18 | 4Sum↗ | Medium | Arrays | arraytwo-pointerssorting |
| 19 | Remove Nth Node From End of List↗ | Medium | Linked List | linked-listtwo-pointers |
| 20 | Valid Parentheses↗ | Easy | Strings | stringstack |
| 21 | Merge Two Sorted Lists↗ | Easy | Linked List | linked-listrecursion |
| 22 | Generate Parentheses↗ | Medium | Backtracking | stringdynamic-programmingbacktracking |
| 23 | Merge k Sorted Lists↗ | Hard | Linked List | linked-listdivide-and-conquerheap-priority-queuemerge-sort |
| 24 | Swap Nodes in Pairs↗ | Medium | Linked List | linked-listrecursion |
| 25 | Reverse Nodes in k-Group↗ | Hard | Strings | linked-listrecursion |
| 26 | Remove Duplicates from Sorted Array↗ | Easy | Arrays | arraytwo-pointers |
| 27 | Remove Element↗ | Easy | Arrays | arraytwo-pointers |
| 28 | Implement strStr()↗ | Easy | Strings | two-pointersstringstring-matching |
| 30 | Substring with Concatenation of All Words↗ | Hard | Strings | hash-tablestringsliding-window |
| 31 | Next Permutation↗ | Medium | Backtracking | arraytwo-pointerspermutation |
| 32 | Longest Valid Parentheses↗ | Hard | Strings | stringdynamic-programmingstack |
| 33 | Search in Rotated Sorted Array↗ | Medium | Arrays | arraybinary-search |
| 34 | Find First and Last Position of Element in Sorted Array↗ | Medium | Arrays | arraybinary-search |
| 35 | Search Insert Position↗ | Easy | Arrays | arraybinary-search |
| 36 | Valid Sudoku↗ | Medium | Matrix | arrayhash-tablematrix |
| 37 | Sudoku Solver↗ | Hard | Matrix | arrayhash-tablebacktrackingmatrix |
| 38 | Count and Say↗ | Medium | Strings | string |
| 39 | Combination Sum↗ | Medium | Backtracking | arraybacktracking |
| 40 | Combination Sum II↗ | Medium | Backtracking | arraybacktracking |
| 41 | First Missing Positive↗ | Hard | Arrays | arrayhash-table |
| 42 | Trapping Rain Water↗ | Hard | Arrays | arraytwo-pointersdynamic-programmingstack |
| 43 | Multiply Strings↗ | Medium | Strings | mathstringsimulation |
| 44 | Wildcard Matching↗ | Hard | Dynamic Programming | stringdynamic-programminggreedyrecursion |
| 45 | Jump Game II↗ | Medium | Greedy | arraydynamic-programminggreedy |
| 46 | Permutations↗ | Medium | Backtracking | backtrackingrecursionarray |
| 47 | Permutations II↗ | Medium | Backtracking | arraybacktrackingsorting |
| 48 | Rotate Image↗ | Medium | Matrix | arraymathmatrix |
| 49 | Group Anagrams↗ | Medium | Strings | arrayhash-tablestringsorting |
| 50 | Pow(x, n)↗ | Medium | Math | mathrecursion |
| 51 | N-Queens↗ | Hard | Backtracking | arraybacktracking |
| 52 | N-Queens II↗ | Hard | Backtracking | backtracking |
| 53 | Maximum Subarray↗ | Medium | Arrays | arraydynamic-programmingdivide-and-conquerkadanes-algorithm |
| 54 | Spiral Matrix↗ | Medium | Matrix | arraymatrixsimulation |
| 55 | Jump Game↗ | Medium | Greedy | arraydynamic-programminggreedy |
| 56 | Merge Intervals↗ | Medium | Sorting | arraysorting |
| 57 | Insert Interval↗ | Medium | Sorting | array |
| 58 | Length of Last Word↗ | Easy | Strings | string |
| 59 | Spiral Matrix II↗ | Medium | Matrix | arraymatrixsimulation |
| 60 | Permutation Sequence↗ | Hard | Math | mathrecursion |
| 61 | Rotate List↗ | Medium | Linked List | linked-listtwo-pointers |
| 62 | Unique Paths↗ | Medium | Dynamic Programming | mathdynamic-programmingcombinatorics |
| 63 | Unique Paths II↗ | Medium | Dynamic Programming | arraydynamic-programmingmatrix |
| 64 | Minimum Path Sum↗ | Medium | Dynamic Programming | arraydynamic-programmingmatrix |
| 65 | Valid Number↗ | Hard | Strings | string |
| 66 | Plus One↗ | Easy | Arrays | arraymath |
| 67 | Add Binary↗ | Easy | Bit Manipulation | mathstringbit-manipulationsimulation |
| 68 | Text Justification↗ | Hard | Strings | arraystringsimulation |
| 69 | Sqrt(x)↗ | Easy | Math | mathbinary-search |
| 70 | Climbing Stairs↗ | Easy | Dynamic Programming | mathdynamic-programmingmemoization |
| 71 | Simplify Path↗ | Medium | Strings | stringstack |
| 72 | Edit Distance↗ | Medium | Dynamic Programming | stringdynamic-programming |
| 73 | Set Matrix Zeroes↗ | Medium | Matrix | arrayhash-tablematrix |
| 74 | Search a 2D Matrix↗ | Medium | Matrix | arraybinary-searchmatrix |
| 75 | Sort Colors↗ | Medium | Sorting | arraytwo-pointerssorting |
| 76 | Minimum Window Substring↗ | Hard | Strings | hash-tablestringsliding-window |
| 77 | Combinations ↗ | Medium | Backtracking | backtracking |
| 78 | Subsets↗ | Medium | Backtracking | arraybacktrackingbit-manipulation |
| 79 | Word Search↗ | Medium | Backtracking | arraystringbacktrackingdepth-first-search |
| 80 | Remove Duplicates from Sorted Array II↗ | Medium | Arrays | arraytwo-pointers |
| 81 | Search in Rotated Sorted Array II↗ | Medium | Arrays | arraybinary-search |
| 82 | Remove Duplicates from Sorted List II↗ | Medium | Linked List | linked-listtwo-pointers |
| 83 | Remove Duplicates from Sorted List↗ | Easy | Linked List | linked-list |
| 84 | Largest Rectangle in Histogram↗ | Hard | Math | arraystackmonotonic-stack |
| 85 | Maximal Rectangle↗ | Hard | Dynamic Programming | arraydynamic-programmingstackmatrix |
| 86 | Partition List↗ | Medium | Dynamic Programming | linked-listtwo-pointers |
| 88 | Merge Sorted Array↗ | Easy | Arrays | arraytwo-pointerssorting |
| 89 | Gray Code↗ | Medium | Bit Manipulation | mathbacktrackingbit-manipulation |
| 90 | Subsets II↗ | Medium | Backtracking | arraybacktrackingbit-manipulation |
| 91 | Decode Ways↗ | Medium | Dynamic Programming | stringdynamic-programming |
| 92 | Reverse Linked List II↗ | Medium | Linked List | linked-list |
| 93 | Restore IP Addresses↗ | Medium | Backtracking | stringbacktracking |
| 94 | Binary Tree Inorder Traversal↗ | Easy | Trees | stacktreedepth-first-searchbinary-tree |
| 95 | Unique Binary Search Trees II↗ | Medium | Trees | dynamic-programmingbacktrackingtreebinary-search-tree |
| 96 | Unique Binary Search Trees↗ | Medium | Trees | mathdynamic-programmingtreebinary-search-tree |
| 98 | Validate Binary Search Tree↗ | Medium | Trees | treedepth-first-searchbinary-search-treebinary-tree |
| 100 | Same Tree↗ | Easy | Trees | treedepth-first-searchbreadth-first-searchbinary-tree |
| 101 | Symmetric Tree↗ | Easy | Trees | treedepth-first-searchbreadth-first-searchbinary-tree |
| 102 | Binary Tree Level Order Traversal↗ | Medium | Trees | treebfsqueue |
| 103 | Binary Tree Zigzag Level Order Traversal↗ | Medium | Trees | treebreadth-first-searchbinary-tree |
| 104 | Maximum Depth of Binary Tree↗ | Easy | Trees | treedepth-first-searchbreadth-first-searchbinary-tree |
| 105 | Construct Binary Tree from Preorder and Inorder Traversal ↗ | Medium | Trees | arrayhash-tabledivide-and-conquertree |
| 106 | Construct Binary Tree from Inorder and Postorder Traversal↗ | Medium | Trees | arrayhash-tabledivide-and-conquertree |
| 107 | Binary Tree Level Order Traversal II↗ | Medium | Trees | treebreadth-first-searchbinary-tree |
| 108 | Convert Sorted Array to Binary Search Tree↗ | Easy | Trees | arraydivide-and-conquertreebinary-search-tree |
| 109 | Convert Sorted List to Binary Search Tree↗ | Medium | Trees | linked-listdivide-and-conquertreebinary-search-tree |
| 110 | Balanced Binary Tree↗ | Easy | Trees | treedepth-first-searchbinary-tree |
| 111 | Minimum Depth of Binary Tree↗ | Easy | Trees | treedepth-first-searchbreadth-first-searchbinary-tree |
| 112 | Path Sum↗ | Easy | Trees | treedepth-first-searchbreadth-first-searchbinary-tree |
| 113 | Path Sum II↗ | Medium | Trees | backtrackingtreedepth-first-searchbinary-tree |
| 114 | Flatten Binary Tree to Linked List↗ | Medium | Trees | linked-liststacktreedepth-first-search |
| 116 | Populating Next Right Pointers in Each Node↗ | Medium | Trees | linked-listtreedepth-first-searchbreadth-first-search |
| 117 | Populating Next Right Pointers in Each Node II↗ | Medium | Trees | linked-listtreedepth-first-searchbreadth-first-search |
| 118 | Pascal's Triangle↗ | Easy | Dynamic Programming | arraydynamic-programming |
| 119 | Pascal's Triangle II↗ | Easy | Dynamic Programming | arraydynamic-programming |
| 120 | Triangle↗ | Medium | Dynamic Programming | arraydynamic-programming |
| 121 | Best Time to Buy and Sell Stock↗ | Easy | Dynamic Programming | arraydynamic-programming |
| 122 | Best Time to Buy and Sell Stock II↗ | Medium | Dynamic Programming | arraydynamic-programminggreedy |
| 123 | Best Time to Buy and Sell Stock III↗ | Hard | Dynamic Programming | arraydynamic-programming |
| 125 | Valid Palindrome↗ | Easy | Strings | two-pointersstring |
| 127 | Word Ladder↗ | Hard | Graph | |
| 128 | Longest Consecutive Sequence↗ | Medium | Arrays | arrayhash-tableunion-find |
| 129 | Sum Root to Leaf Numbers↗ | Medium | Trees | treedepth-first-searchbinary-tree |
| 133 | Clone Graph↗ | Medium | Graph | hash-tabledepth-first-searchbreadth-first-searchgraph |
| 136 | Single Number↗ | Easy | Bit Manipulation | arraybit-manipulation |
| 137 | Single Number II↗ | Medium | Bit Manipulation | arraybit-manipulation |
| 138 | Copy List with Random Pointer↗ | Medium | Math | hash-tablelinked-list |
| 139 | Word Break↗ | Medium | Dynamic Programming | dynamic-programmingstringtriememoization |
| 140 | Word Break II↗ | Hard | Dynamic Programming | arrayhash-tablestringdynamic-programming |
| 141 | Linked List Cycle↗ | Easy | Linked List | hash-tablelinked-listtwo-pointers |
| 142 | Linked List Cycle II↗ | Medium | Linked List | hash-tablelinked-listtwo-pointers |
| 143 | Reorder List↗ | Medium | Linked List | linked-listtwo-pointersstackrecursion |
| 144 | Binary Tree Preorder Traversal↗ | Easy | Trees | stacktreedepth-first-searchbinary-tree |
| 145 | Binary Tree Postorder Traversal↗ | Easy | Trees | stacktreedepth-first-searchbinary-tree |
| 146 | LRU Cache↗ | Medium | Design | hash-tablelinked-listdesigndoubly-linked-list |
| 147 | Insertion Sort List↗ | Medium | Linked List | linked-listsorting |
| 148 | Sort List↗ | Medium | Linked List | linked-listtwo-pointersdivide-and-conquersorting |
| 150 | Evaluate Reverse Polish Notation↗ | Medium | Strings | arraymathstack |
| 151 | Reverse Words in a String↗ | Medium | Strings | two-pointersstring |
| 152 | Maximum Product Subarray↗ | Medium | Arrays | arraydynamic-programming |
| 153 | Find Minimum in Rotated Sorted Array↗ | Medium | Arrays | arraybinary-search |
| 154 | Find Minimum in Rotated Sorted Array II↗ | Hard | Arrays | arraybinary-search |
| 155 | Min Stack↗ | Medium | Design | stackdesign |
| 159 | Longest Substring with At Most Two Distinct Characters↗ | Medium | Strings | hash-tablestringsliding-window |
| 160 | Intersection of Two Linked Lists↗ | Easy | Linked List | hash-tablelinked-listtwo-pointers |
| 162 | Find Peak Element↗ | Medium | Arrays | arraybinary-search |
| 163 | Missing Ranges↗ | Easy | Arrays | array |
| 165 | Compare Version Numbers↗ | Medium | Strings | two-pointersstring |
| 167 | Two Sum II - Input Array Is Sorted↗ | Medium | Arrays | arraytwo-pointersbinary-search |
| 168 | Excel Sheet Column Title↗ | Easy | Math | mathstring |
| 169 | Majority Element↗ | Easy | Arrays | arrayhash-tabledivide-and-conquersorting |
| 171 | Excel Sheet Column Number↗ | Easy | Math | mathstring |
| 173 | Binary Search Tree Iterator↗ | Medium | Trees | stacktreedesignbinary-search-tree |
| 174 | Dungeon Game↗ | Hard | Dynamic Programming | arraydynamic-programmingmatrix |
| 175 | Combine Two Tables↗ | Easy | SQL | database |
| 176 | Second Highest Salary↗ | Medium | SQL | database |
| 177 | Nth Highest Salary↗ | Medium | SQL | database |
| 178 | Rank Scores↗ | Medium | SQL | database |
| 179 | Largest Number↗ | Medium | Sorting | arraystringgreedysorting |
| 180 | Consecutive Numbers↗ | Medium | SQL | database |
| 181 | Employees Earning More Than Their Managers↗ | Easy | SQL | database |
| 182 | Duplicate Emails↗ | Easy | SQL | database |
| 183 | Customers Who Never Order↗ | Easy | SQL | database |
| 184 | Department Highest Salary↗ | Medium | SQL | database |
| 185 | Department Top Three Salaries↗ | Hard | SQL | database |
| 186 | Reverse Words in a String II↗ | Medium | Strings | two-pointersstring |
| 189 | Rotate Array↗ | Medium | Arrays | arraymathtwo-pointers |
| 190 | Reverse Bits↗ | Easy | Bit Manipulation | divide-and-conquerbit-manipulation |
| 191 | Number of 1 Bits↗ | Easy | Bit Manipulation | divide-and-conquerbit-manipulation |
| 192 | Word Frequency↗ | Medium | LeetCode | shell |
| 193 | Valid Phone Numbers↗ | Easy | LeetCode | shell |
| 196 | Delete Duplicate Emails↗ | Easy | SQL | database |
| 197 | Rising Temperature↗ | Easy | SQL | database |
| 198 | House Robber↗ | Medium | Dynamic Programming | arraydynamic-programming |
| 199 | Binary Tree Right Side View↗ | Medium | Trees | treedepth-first-searchbreadth-first-searchbinary-tree |
| 200 | Island Problems↗ | Medium | Graph | graphdfsbfsmatrix |
| 200 | Number of Islands↗ | Medium | Graph | graphdfsbfsmatrix |
| 201 | Bitwise AND of Numbers Range↗ | Medium | Bit Manipulation | bit-manipulation |
| 202 | Happy Number↗ | Easy | Math | hash-tablemathtwo-pointers |
| 203 | Remove Linked List Elements↗ | Easy | Linked List | linked-listrecursion |
| 204 | Count Primes↗ | Medium | Math | arraymathenumerationnumber-theory |
| 205 | Isomorphic Strings↗ | Easy | Strings | hash-tablestring |
| 206 | Reverse Linked List↗ | Easy | Linked List | linked-listrecursion |
| 207 | Course Schedule↗ | Medium | Graph | depth-first-searchbreadth-first-searchgraphtopological-sort |
| 208 | Implement Trie (Prefix Tree)↗ | Medium | Trie | hash-tablestringdesigntrie |
| 209 | Minimum Size Subarray Sum↗ | Medium | Arrays | arraybinary-searchsliding-windowprefix-sum |
| 210 | Course Schedule II↗ | Medium | Graph | depth-first-searchbreadth-first-searchgraphtopological-sort |
| 212 | Word Search II↗ | Hard | Trie | |
| 213 | House Robber II↗ | Medium | Dynamic Programming | arraydynamic-programming |
| 215 | Kth Largest Element in an Array↗ | Medium | Sorting | arraydivide-and-conquersortingheap-priority-queue |
| 216 | Combination Sum III↗ | Medium | Backtracking | arraybacktracking |
| 217 | Contains Duplicate↗ | Easy | Arrays | arrayhash-tablesorting |
| 219 | Contains Duplicate II↗ | Easy | Arrays | arrayhash-tablesliding-window |
| 221 | Maximal Square↗ | Medium | Dynamic Programming | arraydynamic-programmingmatrix |
| 222 | Count Complete Tree Nodes↗ | Easy | Trees | binary-searchbit-manipulationtreebinary-tree |
| 223 | Rectangle Area↗ | Medium | Math | mathgeometry |
| 224 | Basic Calculator↗ | Hard | Stack | mathstringstackrecursion |
| 225 | Implement Stack using Queues↗ | Easy | Design | stackdesignqueue |
| 226 | Invert Binary Tree↗ | Easy | Trees | treedepth-first-searchbreadth-first-searchbinary-tree |
| 227 | Basic Calculator II↗ | Medium | Stack | mathstringstack |
| 228 | Summary Ranges↗ | Easy | Arrays | array |
| 229 | Majority Element II↗ | Medium | Arrays | arrayhash-tablesortingcounting |
| 230 | Kth Smallest Element in a BST↗ | Medium | Trees | treedepth-first-searchbinary-search-treebinary-tree |
| 231 | Power of Two↗ | Easy | Bit Manipulation | mathbit-manipulationrecursion |
| 232 | Implement Queue using Stacks↗ | Easy | Design | stackdesignqueue |
| 234 | Palindrome Linked List↗ | Easy | Linked List | linked-listtwo-pointersstackrecursion |
| 235 | Lowest Common Ancestor of a Binary Search Tree↗ | Medium | Trees | treedepth-first-searchbinary-search-treebinary-tree |
| 236 | Lowest Common Ancestor of a Binary Tree↗ | Medium | Trees | treedepth-first-searchbinary-tree |
| 237 | Delete Node in a Linked List↗ | Medium | Linked List | linked-list |
| 238 | Product of Array Except Self↗ | Medium | Arrays | arrayprefix-sum |
| 239 | Sliding Window Maximum↗ | Hard | Arrays | arrayqueuesliding-windowheap-priority-queue |
| 240 | Search a 2D Matrix II↗ | Medium | Matrix | arraybinary-searchdivide-and-conquermatrix |
| 242 | Valid Anagram↗ | Easy | Strings | hash-tablestringsorting |
| 243 | Shortest Word Distance↗ | Easy | Strings | arraystring |
| 244 | Shortest Word Distance II↗ | Medium | Design | arrayhash-tabletwo-pointersstring |
| 245 | Shortest Word Distance III↗ | Medium | Strings | arraystring |
| 249 | Group Shifted Strings↗ | Medium | Strings | arrayhash-tablestring |
| 250 | Count Univalue Subtrees↗ | Medium | Trees | treedepth-first-searchbinary-tree |
| 252 | Meeting Rooms↗ | Easy | Sorting | arraysorting |
| 253 | Meeting Rooms II↗ | Medium | Sorting | arraytwo-pointersgreedysorting |
| 255 | Verify Preorder Sequence in Binary Search Tree↗ | Medium | Trees | arraystacktreebinary-search-tree |
| 257 | Binary Tree Paths↗ | Easy | Trees | stringbacktrackingtreedepth-first-search |
| 258 | Add Digits↗ | Easy | Math | mathsimulationnumber-theory |
| 261 | Graph Valid Tree↗ | Medium | Graph | depth-first-searchbreadth-first-searchunion-findgraph |
| 263 | Ugly Number↗ | Easy | Math | math |
| 266 | Palindrome Permutation↗ | Easy | Strings | hash-tablestringbit-manipulation |
| 268 | Missing Number↗ | Easy | Bit Manipulation | arrayhash-tablemathbinary-search |
| 270 | Closest Binary Search Tree Value↗ | Easy | Trees | binary-searchtreedepth-first-searchbinary-search-tree |
| 271 | Encode and Decode Strings↗ | Medium | Strings | arraystringdesign |
| 273 | Integer to English Words↗ | Hard | Strings | mathstringrecursion |
| 274 | H-Index↗ | Medium | Sorting | arraysortingcounting-sort |
| 275 | H-Index II↗ | Medium | Sorting | arraybinary-search |
| 277 | Find the Celebrity↗ | Medium | Graph | two-pointersgraphinteractive |
| 278 | First Bad Version↗ | Easy | Arrays | binary-searchinteractive |
| 279 | Perfect Squares↗ | Medium | Dynamic Programming | mathdynamic-programmingbreadth-first-search |
| 280 | Wiggle Sort↗ | Medium | Sorting | arraygreedysorting |
| 283 | Move Zeroes↗ | Easy | Arrays | arraytwo-pointers |
| 285 | Inorder Successor in BST↗ | Medium | Trees | treedepth-first-searchbinary-search-treebinary-tree |
| 286 | Walls and Gates↗ | Medium | Matrix | arraybreadth-first-searchmatrix |
| 290 | Word Pattern↗ | Easy | Strings | hash-tablestring |
| 295 | Find Median from Data Stream↗ | Hard | Sorting | two-pointersdesignsortingheap-priority-queue |
| 297 | Serialize and Deserialize Binary Tree↗ | Hard | Trees | stringtreedepth-first-searchbreadth-first-search |
| 298 | Binary Tree Longest Consecutive Sequence↗ | Medium | Trees | treedepth-first-searchbinary-tree |
| 303 | Range Sum Query - Immutable↗ | Easy | Design | arraydesignprefix-sum |
| 304 | Range Sum Query 2D - Immutable↗ | Medium | Design | arraydesignmatrixprefix-sum |
| 307 | Range Sum Query - Mutable↗ | Medium | Design | arraydivide-and-conquerdesignbinary-indexed-tree |
| 312 | Burst Balloons↗ | Hard | Dynamic Programming | arraydynamic-programming |
| 314 | Binary Tree Vertical Order Traversal↗ | Medium | Trees | hash-tabletreedepth-first-searchbreadth-first-search |
| 318 | Maximum Product of Word Lengths↗ | Medium | SQL | arraystringbit-manipulation |
| 319 | Bulb Switcher↗ | Medium | Math | mathbrainteaser |
| 322 | Coin Change↗ | Medium | Dynamic Programming | dynamic-programmingarraybfs |
| 323 | Number of Connected Components in an Undirected Graph↗ | Medium | Graph | depth-first-searchbreadth-first-searchunion-findgraph |
| 324 | Wiggle Sort II↗ | Medium | Sorting | arraydivide-and-conquergreedysorting |
| 325 | Maximum Size Subarray Sum Equals k↗ | Medium | Arrays | arrayhash-tableprefix-sum |
| 326 | Power of Three↗ | Easy | Bit Manipulation | mathrecursion |
| 328 | Odd Even Linked List↗ | Medium | Linked List | linked-list |
| 329 | Longest Increasing Path in a Matrix↗ | Hard | Matrix | arraydynamic-programmingdepth-first-searchbreadth-first-search |
| 332 | Reconstruct Itinerary↗ | Hard | Graph | arraystringdepth-first-searchgraph |
| 337 | House Robber III↗ | Medium | Dynamic Programming | dynamic-programmingtreedepth-first-searchbinary-tree |
| 338 | Counting Bits↗ | Easy | Bit Manipulation | dynamic-programmingbit-manipulation |
| 340 | Longest Substring with At Most K Distinct Characters↗ | Medium | Strings | hash-tablestringsliding-window |
| 342 | Power of Four↗ | Easy | Bit Manipulation | mathbit-manipulationrecursion |
| 344 | Reverse String↗ | Easy | Strings | two-pointersstring |
| 345 | Reverse Vowels of a String↗ | Easy | Strings | two-pointersstring |
| 346 | Moving Average from Data Stream↗ | Easy | Design | arraydesignqueuedata-stream |
| 347 | Top K Frequent Elements↗ | Medium | Sorting | arrayhash-tabledivide-and-conquersorting |
| 349 | Intersection of Two Arrays↗ | Easy | Linked List | arrayhash-tabletwo-pointersbinary-search |
| 350 | Intersection of Two Arrays II↗ | Easy | Linked List | arrayhash-tabletwo-pointersbinary-search |
| 357 | Count Numbers with Unique Digits↗ | Medium | Dynamic Programming | mathdynamic-programmingbacktracking |
| 359 | Logger Rate Limiter↗ | Easy | Design | hash-tabledesigndata-stream |
| 366 | Find Leaves of Binary Tree↗ | Medium | Trees | treedepth-first-searchbinary-tree |
| 374 | Guess Number Higher or Lower↗ | Easy | Arrays | binary-searchinteractive |
| 383 | Ransom Note↗ | Easy | Strings | hash-tablestringcounting |
| 384 | Shuffle an Array↗ | Medium | Math | arraymathdesignrandomized |
| 387 | First Unique Character in a String↗ | Easy | Strings | hash-tablestringqueuecounting |
| 394 | Decode String↗ | Medium | Strings | stringstackrecursion |
| 395 | Longest Substring with At Least K Repeating Characters↗ | Medium | Strings | hash-tablestringdivide-and-conquersliding-window |
| 402 | Remove K Digits↗ | Medium | Greedy | stringstackgreedymonotonic-stack |
| 403 | Frog Jump↗ | Hard | Dynamic Programming | arraydynamic-programming |
| 409 | Longest Palindrome↗ | Easy | Strings | hash-tablestringgreedy |
| 412 | Fizz Buzz↗ | Easy | Math | mathstringsimulation |
| 413 | Arithmetic Slices↗ | Medium | Dynamic Programming | arraydynamic-programmingsliding-window |
| 415 | Add Strings↗ | Easy | Strings | mathstringsimulation |
| 416 | Partition Equal Subset Sum↗ | Medium | Dynamic Programming | arraydynamic-programming |
| 419 | Battleships in a Board↗ | Medium | Matrix | arraydepth-first-searchmatrix |
| 424 | Longest Repeating Character Replacement↗ | Medium | Strings | hash-tablestringsliding-window |
| 442 | Find All Duplicates in an Array↗ | Medium | Arrays | arrayhash-tablesorting |
| 443 | String Compression↗ | Medium | Strings | two-pointersstring |
| 445 | Add Two Numbers II↗ | Medium | Linked List | linked-listmathstack |
| 448 | Find All Numbers Disappeared in an Array↗ | Easy | Arrays | arrayhash-table |
| 449 | Serialize and Deserialize BST↗ | Medium | Trees | stringtreedepth-first-searchbreadth-first-search |
| 450 | Delete Node in a BST↗ | Medium | Trees | treebinary-search-treebinary-tree |
| 451 | Sort Characters By Frequency↗ | Medium | Heap | hash-tablestringsortingheap-priority-queue |
| 453 | Minimum Moves to Equal Array Elements↗ | Medium | Math | arraymath |
| 459 | Repeated Substring Pattern↗ | Easy | Strings | stringstring-matching |
| 461 | Hamming Distance↗ | Easy | Bit Manipulation | bit-manipulation |
| 462 | Minimum Moves to Equal Array Elements II↗ | Medium | Math | arraymathsorting |
| 463 | Island Perimeter↗ | Easy | Matrix | arraydepth-first-searchbreadth-first-searchmatrix |
| 473 | Matchsticks to Square↗ | Medium | Backtracking | arraydynamic-programmingbacktrackingbit-manipulation |
| 475 | Heaters↗ | Medium | Arrays | arraytwo-pointersbinary-searchsorting |
| 477 | Total Hamming Distance↗ | Medium | Bit Manipulation | arraymathbit-manipulation |
| 480 | Sliding Window Median↗ | Hard | Sorting | arrayhash-tablesliding-windowheap-priority-queue |
| 485 | Max Consecutive Ones↗ | Easy | Arrays | array |
| 487 | Max Consecutive Ones II↗ | Medium | Arrays | arraydynamic-programmingsliding-window |
| 490 | The Maze↗ | Medium | Graph | arraydepth-first-searchbreadth-first-searchmatrix |
| 494 | Target Sum↗ | Medium | Dynamic Programming | arraydynamic-programmingbacktracking |
| 495 | Teemo Attacking↗ | Easy | Greedy | arraysimulation |
| 496 | Next Greater Element I↗ | Easy | Stack | arrayhash-tablestackmonotonic-stack |
| 498 | Diagonal Traverse↗ | Medium | Matrix | arraymatrixsimulation |
| 500 | Keyboard Row↗ | Easy | Dynamic Programming | arrayhash-tablestring |
| 503 | Next Greater Element II↗ | Medium | Stack | arraystackmonotonic-stack |
| 506 | Relative Ranks↗ | Easy | Sorting | arraysortingheap-priority-queue |
| 513 | Find Bottom Left Tree Value↗ | Medium | Trees | treedepth-first-searchbreadth-first-searchbinary-tree |
| 515 | Find Largest Value in Each Tree Row↗ | Medium | Trees | treedepth-first-searchbreadth-first-searchbinary-tree |
| 516 | Longest Palindromic Subsequence↗ | Medium | Dynamic Programming | stringdynamic-programming |
| 525 | Contiguous Array↗ | Medium | Arrays | arrayhash-tableprefix-sum |
| 530 | Minimum Absolute Difference in BST↗ | Easy | Trees | treedepth-first-searchbreadth-first-searchbinary-search-tree |
| 532 | K-diff Pairs in an Array↗ | Medium | Arrays | arrayhash-tabletwo-pointersbinary-search |
| 535 | Encode and Decode TinyURL↗ | Medium | Design | hash-tablestringdesignhash-function |
| 540 | Single Element in a Sorted Array↗ | Medium | Arrays | arraybinary-search |
| 541 | Reverse String II↗ | Easy | Strings | two-pointersstring |
| 542 | 01 Matrix↗ | Medium | Matrix | arraydynamic-programmingbreadth-first-searchmatrix |
| 543 | Diameter of Binary Tree↗ | Easy | Trees | treedepth-first-searchbinary-tree |
| 545 | Boundary of Binary Tree↗ | Medium | Trees | treedepth-first-searchbinary-tree |
| 547 | Number of Provinces↗ | Medium | Graph | depth-first-searchbreadth-first-searchunion-findgraph |
| 556 | Next Greater Element III↗ | Medium | Stack | mathtwo-pointersstring |
| 557 | Reverse Words in a String III↗ | Easy | Strings | two-pointersstring |
| 560 | Subarray Sum Equals K↗ | Medium | Arrays | arrayhash-tableprefix-sum |
| 563 | Binary Tree Tilt↗ | Easy | Trees | treedepth-first-searchbinary-tree |
| 566 | Reshape the Matrix↗ | Easy | Matrix | arraymatrixsimulation |
| 570 | Managers with at Least 5 Direct Reports↗ | Medium | SQL | database |
| 572 | Subtree of Another Tree↗ | Easy | Trees | treedepth-first-searchstring-matchingbinary-tree |
| 574 | Winning Candidate↗ | Medium | SQL | database |
| 577 | Employee Bonus↗ | Easy | SQL | database |
| 580 | Count Student Number in Departments↗ | Medium | SQL | database |
| 584 | Find Customer Referee↗ | Easy | SQL | database |
| 586 | Customer Placing the Largest Number of Orders↗ | Easy | Sorting | database |
| 595 | Big Countries↗ | Easy | Trie | database |
| 596 | Classes More Than 5 Students↗ | Easy | SQL | database |
| 605 | Can Place Flowers↗ | Easy | Greedy | arraygreedy |
| 611 | Valid Triangle Number↗ | Medium | Dynamic Programming | arraytwo-pointersbinary-searchgreedy |
| 617 | Merge Two Binary Trees↗ | Easy | Trees | treedepth-first-searchbreadth-first-searchbinary-tree |
| 619 | Biggest Single Number↗ | Easy | Bit Manipulation | database |
| 620 | Not Boring Movies↗ | Easy | SQL | database |
| 621 | Task Scheduler↗ | Medium | Greedy | arrayhash-tablegreedysorting |
| 627 | Swap Salary↗ | Easy | SQL | database |
| 628 | Maximum Product of Three Numbers↗ | Easy | SQL | arraymathsorting |
| 633 | Sum of Square Numbers↗ | Medium | Math | mathtwo-pointersbinary-search |
| 637 | Average of Levels in Binary Tree↗ | Easy | Trees | treedepth-first-searchbreadth-first-searchbinary-tree |
| 643 | Maximum Average Subarray I↗ | Easy | Arrays | arraysliding-window |
| 647 | Palindromic Substrings↗ | Medium | Strings | two-pointersstringdynamic-programming |
| 658 | Find K Closest Elements↗ | Medium | Arrays | arraytwo-pointersbinary-searchsliding-window |
| 671 | Second Minimum Node In a Binary Tree↗ | Easy | Trees | treedepth-first-searchbinary-tree |
| 678 | Valid Parenthesis String↗ | Medium | Strings | stringdynamic-programmingstackgreedy |
| 680 | Valid Palindrome II↗ | Easy | Strings | two-pointersstringgreedy |
| 682 | Baseball Game↗ | Easy | Stack | arraystacksimulation |
| 692 | Top K Frequent Words↗ | Medium | Sorting | arrayhash-tablestringtrie |
| 694 | Number of Distinct Islands↗ | Medium | Graph | arrayhash-tabledepth-first-searchbreadth-first-search |
| 695 | Max Area of Island↗ | Medium | Graph | arraydepth-first-searchbreadth-first-searchunion-find |
| 696 | Count Binary Substrings↗ | Easy | Strings | two-pointersstring |
| 698 | Partition to K Equal Sum Subsets↗ | Medium | Dynamic Programming | arraydynamic-programmingbacktrackingbit-manipulation |
| 713 | Subarray Product Less Than K↗ | Medium | Arrays | arraybinary-searchsliding-windowprefix-sum |
| 718 | Maximum Length of Repeated Subarray↗ | Medium | Arrays | arraybinary-searchdynamic-programmingsliding-window |
| 724 | Pivot Index↗ | Easy | Arrays | arrayprefix-sum |
| 727 | Minimum Window Subsequence↗ | Hard | Dynamic Programming | stringdynamic-programmingsliding-window |
| 733 | Flood Fill↗ | Easy | Graph | arraydepth-first-searchbreadth-first-searchmatrix |
| 735 | Asteroid Collision↗ | Medium | Stack | arraystacksimulation |
| 739 | Daily Temperatures↗ | Medium | SQL | arraystackmonotonic-stack |
| 747 | Min Cost Climbing Stairs↗ | Easy | Dynamic Programming | arraydynamic-programming |
| 753 | Open the Lock↗ | Medium | Graph | arrayhash-tablestringbreadth-first-search |
| 758 | Convert Binary Search Tree to Sorted Doubly Linked List↗ | Medium | Trees | linked-liststacktreedepth-first-search |
| 764 | N-ary Tree Level Order Traversal↗ | Medium | Trees | treebreadth-first-search |
| 765 | Serialize and Deserialize N-ary Tree↗ | Hard | Trees | stringtreedepth-first-searchbreadth-first-search |
| 767 | Prime Number of Set Bits in Binary Representation↗ | Easy | Bit Manipulation | mathbit-manipulation |
| 774 | Maximum Depth of N-ary Tree↗ | Easy | Trees | treedepth-first-searchbreadth-first-search |
| 775 | N-ary Tree Preorder Traversal↗ | Easy | Trees | stacktreedepth-first-search |
| 776 | N-ary Tree Postorder Traversal↗ | Easy | Trees | stacktreedepth-first-search |
| 777 | Toeplitz Matrix↗ | Easy | Matrix | arraymatrix |
| 778 | Reorganize String↗ | Medium | Strings | hash-tablestringgreedysorting |
| 783 | Search in a Binary Search Tree↗ | Easy | Trees | treebinary-search-treebinary-tree |
| 784 | Insert into a Binary Search Tree↗ | Medium | Trees | treebinary-search-treebinary-tree |
| 785 | Basic Calculator III↗ | Hard | Stack | mathstringstackrecursion |
| 786 | Search in a Sorted Array of Unknown Size↗ | Medium | Arrays | arraybinary-searchinteractive |
| 789 | Kth Largest Element in a Stream↗ | Easy | Sorting | treedesignbinary-search-treeheap-priority-queue |
| 791 | Split BST↗ | Medium | Trees | treebinary-search-treerecursionbinary-tree |
| 792 | Binary Search↗ | Easy | Arrays | arraybinary-search |
| 795 | K-th Symbol in Grammar↗ | Medium | Math | mathbit-manipulationrecursion |
| 799 | Minimum Distance Between BST Nodes↗ | Easy | Trees | treedepth-first-searchbreadth-first-searchbinary-search-tree |
| 800 | Letter Case Permutation↗ | Medium | Backtracking | stringbacktrackingbit-manipulation |
| 812 | Rotate String↗ | Easy | Strings | stringstring-matching |
| 837 | Most Common Word↗ | Easy | Strings | arrayhash-tablestringcounting |
| 860 | Design Circular Queue↗ | Medium | Design | arraylinked-listdesignqueue |
| 863 | Sum of Distances in Tree↗ | Hard | Trees | dynamic-programmingtreedepth-first-searchgraph |
| 866 | Rectangle Overlap↗ | Easy | Math | mathgeometry |
| 871 | Keys and Rooms↗ | Medium | Graph | depth-first-searchbreadth-first-searchgraph |
| 878 | Shifting Letters↗ | Medium | Strings | arraystringprefix-sum |
| 889 | Buddy Strings↗ | Easy | Strings | hash-tablestring |
| 893 | All Nodes Distance K in Binary Tree↗ | Medium | Trees | hash-tabletreedepth-first-searchbreadth-first-search |
| 898 | Transpose Matrix↗ | Easy | Matrix | arraymatrixsimulation |
| 899 | Binary Gap↗ | Easy | Sorting | bit-manipulation |
| 902 | Minimum Number of Refueling Stops↗ | Hard | Dynamic Programming | arraydynamic-programminggreedyheap-priority-queue |
| 908 | Middle of the Linked List↗ | Easy | Linked List | linked-listtwo-pointers |
| 948 | Sort an Array↗ | Medium | Sorting | arraydivide-and-conquersortingheap-priority-queue |
| 951 | Partition Array into Disjoint Intervals↗ | Medium | Dynamic Programming | array |
| 957 | Minimum Add to Make Parentheses Valid↗ | Medium | Strings | stringstackgreedy |
| 965 | Unique Email Addresses↗ | Easy | SQL | arrayhash-tablestring |
| 974 | Reorder Data in Log Files↗ | Medium | SQL | arraystringsorting |
| 975 | Range Sum of BST↗ | Easy | Trees | treedepth-first-searchbinary-search-treebinary-tree |
| 976 | Minimum Area Rectangle↗ | Medium | Math | arrayhash-tablemathgeometry |
| 979 | DI String Match↗ | Easy | Strings | arraytwo-pointersstringgreedy |
| 991 | Array of Doubled Pairs↗ | Medium | Greedy | arrayhash-tablegreedysorting |
| 998 | Check Completeness of a Binary Tree↗ | Medium | Trees | treebreadth-first-searchbinary-tree |
| 1005 | Univalued Binary Tree↗ | Easy | Trees | treedepth-first-searchbreadth-first-searchbinary-tree |
| 1008 | Binary Tree Cameras↗ | Hard | Trees | dynamic-programmingtreedepth-first-searchbinary-tree |
| 1013 | Fibonacci Number↗ | Easy | Math | mathdynamic-programmingrecursionmemoization |
| 1014 | K Closest Points to Origin↗ | Medium | Heap | arraymathdivide-and-conquergeometry |
| 1019 | Squares of a Sorted Array↗ | Easy | Arrays | arraytwo-pointerssorting |
| 1020 | Longest Turbulent Subarray↗ | Medium | Arrays | arraydynamic-programmingsliding-window |
| 1021 | Distribute Coins in Binary Tree↗ | Medium | Trees | treedepth-first-searchbinary-tree |
| 1026 | String Without AAA or BBB↗ | Medium | Strings | stringgreedy |
| 1028 | Interval List Intersections↗ | Medium | Linked List | arraytwo-pointersline-sweep |
| 1029 | Vertical Order Traversal of a Binary Tree↗ | Hard | Trees | hash-tabletreedepth-first-searchbreadth-first-search |
| 1030 | Smallest String Starting From Leaf↗ | Medium | Strings | stringbacktrackingtreedepth-first-search |
| 1034 | Subarrays with K Different Integers↗ | Hard | Arrays | arrayhash-tablesliding-windowcounting |
| 1035 | Cousins in Binary Tree↗ | Easy | Trees | treedepth-first-searchbreadth-first-searchbinary-tree |
| 1039 | Find the Town Judge↗ | Easy | Graph | arrayhash-tablegraph |
| 1046 | Max Consecutive Ones III↗ | Medium | Arrays | arraybinary-searchsliding-windowprefix-sum |
| 1054 | Complement of Base 10 Integer↗ | Easy | Math | bit-manipulation |
| 1081 | Video Stitching↗ | Medium | Greedy | arraydynamic-programminggreedy |
| 1102 | Check If a Number Is Majority Element in a Sorted Array↗ | Easy | Arrays | arraybinary-search |
| 1107 | Minimum Swaps to Group All 1's Together↗ | Medium | Arrays | arraysliding-window |
| 1149 | Intersection of Three Sorted Arrays↗ | Easy | Linked List | arrayhash-tablebinary-searchcounting |
| 1150 | Two Sum BSTs↗ | Medium | Trees | two-pointersbinary-searchstacktree |
| 1217 | Relative Sort Array↗ | Easy | Sorting | arrayhash-tablesortingcounting-sort |
| 1222 | Remove Covered Intervals↗ | Medium | Sorting | arraysorting |
| 1241 | Decompress Run-Length Encoded List↗ | Easy | Arrays | array |
| 1250 | Longest Common Subsequence↗ | Medium | Dynamic Programming | stringdynamic-programming |
| 1254 | Deepest Leaves Sum↗ | Medium | Trees | treedepth-first-searchbreadth-first-searchbinary-tree |
| 1267 | Remove Zero Sum Consecutive Nodes from Linked List↗ | Medium | Linked List | hash-tablelinked-list |
| 1288 | Maximum Subarray Sum with One Deletion↗ | Medium | Arrays | arraydynamic-programming |
| 1297 | Maximum Number of Balloons↗ | Easy | Dynamic Programming | hash-tablestringcounting |
| 1304 | Longest Happy String↗ | Medium | Strings | stringgreedyheap-priority-queue |
| 1349 | Check If It Is a Straight Line↗ | Easy | Math | arraymathgeometry |
| 1360 | Maximum Length of a Concatenated String with Unique Characters↗ | Medium | Strings | arraystringbacktrackingbit-manipulation |
| 1370 | Count Number of Nice Subarrays↗ | Medium | Arrays | arrayhash-tablemathsliding-window |
| 1380 | Number of Closed Islands↗ | Medium | Graph | arraydepth-first-searchbreadth-first-searchunion-find |
| 1391 | Counting Elements↗ | Easy | Arrays | arrayhash-table |
| 1400 | Find Winner on a Tic Tac Toe Game↗ | Easy | Matrix | arrayhash-tablematrixsimulation |
| 1426 | Find N Unique Integers Sum up to Zero↗ | Easy | Math | arraymath |
| 1428 | Jump Game III↗ | Medium | Greedy | arraydepth-first-searchbreadth-first-search |
| 1437 | Minimum Insertion Steps to Make a String Palindrome↗ | Hard | Strings | stringdynamic-programming |
| 1444 | Number of Steps to Reduce a Number to Zero↗ | Easy | Strings | mathbit-manipulation |
| 1446 | Angle Between Hands of a Clock↗ | Medium | Math | math |
| 1451 | Minimum Number of Taps to Open to Water a Garden↗ | Hard | Dynamic Programming | arraydynamic-programminggreedy |
| 1458 | Sort Integers by The Number of 1 Bits↗ | Easy | Bit Manipulation | arraybit-manipulationsortingcounting |
| 1460 | Number of Substrings Containing All Three Characters↗ | Medium | Strings | hash-tablestringsliding-window |
| 1468 | Check If N and Its Double Exist↗ | Easy | Arrays | arrayhash-tabletwo-pointersbinary-search |
| 1487 | Cinema Seat Allocation↗ | Medium | SQL | arrayhash-tablegreedybit-manipulation |
| 1494 | Activity Participants↗ | Medium | SQL | database |
| 1509 | Replace Employee ID With The Unique Identifier↗ | Easy | SQL | database |
| 1544 | Count Good Nodes in Binary Tree↗ | Medium | Trees | treedepth-first-searchbreadth-first-searchbinary-tree |
| 1570 | Final Prices With a Special Discount in a Shop↗ | Easy | Stack | arraystackmonotonic-stack |
| 1609 | Find All The Lonely Nodes↗ | Easy | Trees | treedepth-first-searchbreadth-first-searchbinary-tree |
| 1635 | Number of Good Pairs↗ | Easy | Math | arrayhash-tablemathcounting |
| 1636 | Number of Substrings With Only 1s↗ | Medium | Strings | mathstring |
| 1646 | Kth Missing Positive Number↗ | Easy | Arrays | arraybinary-search |
| 1648 | Minimum Insertions to Balance a Parentheses String↗ | Medium | Strings | stringstackgreedy |
| 1677 | Matrix Diagonal Sum↗ | Easy | Matrix | arraymatrix |
| 1700 | Minimum Time to Make Rope Colorful↗ | Medium | Greedy | arraystringdynamic-programminggreedy |
| 1720 | Crawler Log Folder↗ | Easy | Stack | arraystringstack |
| 1738 | Maximal Network Rank↗ | Medium | Graph | graph |
| 1770 | Minimum Deletions to Make Character Frequencies Unique↗ | Medium | Greedy | hash-tablestringgreedysorting |
| 1776 | Minimum Operations to Reduce X to Zero↗ | Medium | Arrays | arrayhash-tablebinary-searchsliding-window |
| 1777 | Determine if Two Strings Are Close↗ | Medium | Strings | hash-tablestringsortingcounting |
| 1787 | Sum of Absolute Differences in a Sorted Array↗ | Medium | Math | arraymathprefix-sum |
| 1794 | Minimize Deviation in Array↗ | Hard | Heap | arraygreedyheap-priority-queueordered-set |
| 1796 | Correct a Binary Tree↗ | Medium | Trees | hash-tabletreedepth-first-searchbreadth-first-search |
| 1805 | Minimum Adjacent Swaps for K Consecutive Ones↗ | Hard | Greedy | arraygreedysliding-windowprefix-sum |
| 1829 | Maximum Units on a Truck↗ | Easy | Greedy | arraygreedysorting |
| 1848 | Sum of Unique Elements↗ | Easy | Arrays | arrayhash-tablecounting |
| 1885 | Count Number of Homogenous Substrings↗ | Medium | Strings | mathstring |
| 1915 | Check if One String Swap Can Make Strings Equal↗ | Easy | Strings | hash-tablestringcounting |
| 1919 | Sort Features by Popularity↗ | Medium | Sorting | arrayhash-tablestringsorting |
| 1950 | Sign of the Product of an Array↗ | Easy | SQL | arraymath |
| 1954 | Replace All Digits with Characters↗ | Easy | Strings | string |
| 1997 | Next Palindrome Using Same Digits↗ | Hard | Strings | two-pointersstring |
| 2035 | Count Sub Islands↗ | Medium | Graph | arraydepth-first-searchbreadth-first-searchunion-find |
| 2053 | Check if All Characters Have Equal Number of Occurrences↗ | Easy | Strings | hash-tablestringcounting |
| 2083 | Three Divisors↗ | Easy | Math | mathenumerationnumber-theory |
| 2095 | Minimum Number of Swaps to Make the String Balanced↗ | Medium | Strings | two-pointersstringstackgreedy |
| 2107 | Find Unique Binary String↗ | Medium | Strings | arrayhash-tablestringbacktracking |
| 2113 | Find the Kth Largest Integer in the Array↗ | Medium | Sorting | arraystringdivide-and-conquersorting |
| 2116 | Count Number of Pairs With Absolute Difference K↗ | Easy | Arrays | arrayhash-tablecounting |
| 2117 | Find Original Array From Doubled Array↗ | Medium | Greedy | arrayhash-tablegreedysorting |
| 2121 | Find if Path Exists in Graph↗ | Easy | Graph | depth-first-searchbreadth-first-searchunion-findgraph |
| 2137 | Final Value of Variable After Performing Operations↗ | Easy | Strings | arraystringsimulation |
| 2138 | Sum of Beauty in the Array↗ | Medium | Arrays | array |
| 2181 | Smallest Index With Equal Value↗ | Easy | Arrays | array |
| 2210 | Find Target Indices After Sorting Array↗ | Easy | Sorting | arraybinary-searchsorting |
| 2211 | K Radius Subarray Averages↗ | Medium | Arrays | arraysliding-window |
| 2216 | Delete the Middle Node of a Linked List↗ | Medium | Linked List | linked-listtwo-pointers |
| 2225 | Substrings That Begin and End With the Same Letter↗ | Medium | Strings | hash-tablemathstringcounting |
| 2231 | Find First Palindromic String in the Array↗ | Easy | Strings | arraytwo-pointersstring |
| 2233 | Number of Smooth Descent Periods of a Stock↗ | Medium | Dynamic Programming | arraymathtwo-pointersdynamic-programming |
| 2236 | Maximum Twin Sum of a Linked List↗ | Medium | Linked List | linked-listtwo-pointersstack |
| 2238 | A Number After a Double Reversal↗ | Easy | Math | math |
| 2241 | Recover the Original Array↗ | Hard | Arrays | arrayhash-tabletwo-pointerssorting |
| 2243 | Check if All A's Appears Before All B's↗ | Easy | Strings | string |
| 2245 | Destroying Asteroids↗ | Medium | Greedy | arraygreedysorting |
| 2284 | Smallest Value of the Rearranged Number↗ | Medium | Math | mathsorting |
| 2288 | Count Operations to Obtain Zero↗ | Easy | Math | mathsimulation |
| 2290 | Removing Minimum Number of Magic Beans↗ | Medium | Greedy | arraygreedysortingenumeration |
| 2298 | Count Integers With Even Digit Sum↗ | Easy | Math | mathsimulation |
| 2383 | Add Two Integers↗ | Easy | Math | math |
| — | Permutations II (Unique) | — | Backtracking | |
| — | Sorting Algorithms | — | Sorting | |
| — | String Permutations | — | Strings |