Study
Question Library
Every coding question we've collected, from the Peralta 75 to problems companies were reported asking. Pick one and practice it.
257 questions
- 3SumSorting + Two PointersMedium
- 16. 3Sum ClosestTwo PointersMedium
- 721. Accounts MergeUnion FindMedium
- 415. Add StringsString ManipulationEasy
- 2. Add Two NumbersLinked List ManipulationMedium
- 3021. Alice and Bob Playing Flower GameMathMedium
- 269. Alien DictionaryTopological SortHard
- 432. All O`one Data StructureDoubly Linked List + Hash MapHard
- 2385. Amount of Time for Binary Tree to Be InfectedBFSMedium
- Anagram NumberSortingEasy
- Array BurstStackMedium
- Assign Tasks to WorkersHeapMedium
- 735. Asteroid CollisionStackMedium
- 844. Backspace String CompareTwo PointersEasy
- 110. Balanced Binary TreeDFSEasy
- Banking SystemHash MapMedium
- 224. Basic CalculatorStackHard
- 227. Basic Calculator IIStackMedium
- 121. Best Time to Buy and Sell StockGreedyEasy
- 123. Best Time to Buy and Sell Stock IIIDynamic ProgrammingHard
- Binary Addition CalculatorDigit-by-Digit AdditionEasy
- 968. Binary Tree CamerasDFSHard
- 124. Binary Tree Maximum Path SumDFSHard
- 199. Binary Tree Right Side ViewBFSMedium
- Block MiningDynamic ProgrammingHard
- Bowling ScoreSimulationMedium
- 1328. Break a PalindromeGreedyMedium
- 312. Burst BalloonsDynamic ProgrammingHard
- 815. Bus RoutesBFSHard
- 605. Can Place FlowersGreedyEasy
- 135. CandyGreedyHard
- 787. Cheapest Flights Within K StopsBellman-FordMedium
- Cheapest Server RoutePrefix SumMedium
- CIDR Access RulesBit ManipulationMedium
- Circular PrinterGreedyEasy
- 70. Climbing StairsDynamic ProgrammingEasy
- 2523. Closest Prime Numbers in RangeMathMedium
- 322. Coin ChangeDynamic ProgrammingMedium
- 216. Combination Sum IIIBacktrackingMedium
- 77. CombinationsBacktrackingMedium
- 165. Compare Version NumbersString ManipulationMedium
- 472. Concatenated WordsDynamic ProgrammingHard
- Container With Most WaterTwo PointersMedium
- 219. Contains Duplicate IISliding WindowEasy
- 315. Count of Smaller Numbers After SelfBinary SearchHard
- Count Pairs Matching Sum and Difference ConditionsHash MapMedium
- 338. Counting BitsDynamic ProgrammingEasy
- 210. Course Schedule IITopological SortMedium
- 993. Cousins in Binary TreeBFSEasy
- 1192. Critical Connections in a NetworkDFSHard
- 739. Daily TemperaturesMonotonic StackMedium
- 394. Decode StringStackMedium
- Dependency ResolverDependency modelling · orderingMedium
- 211. Design Add and Search Words Data StructureTrieMedium
- 631. Design Excel Sum FormulaTopological SortHard
- 588. Design In-Memory File SystemTrieHard
- Detect Edge Pixels in a 2D ImageMatrix TraversalEasy
- 1424. Diagonal Traverse IIMatrixMedium
- 543. Diameter of Binary TreeDFSEasy
- 1223. Dice Roll SimulationDynamic ProgrammingHard
- 115. Distinct SubsequencesDynamic ProgrammingHard
- 174. Dungeon GameDynamic ProgrammingHard
- 399. Evaluate DivisionDFSMedium
- 448. Find All Numbers Disappeared in an ArrayArray ManipulationEasy
- 34. Find First and Last Position of Element in Sorted ArrayBinary SearchMedium
- 1971. Find if Path Exists in GraphUnion FindEasy
- 515. Find Largest Value in Each Tree RowBFSMedium
- 295. Find Median from Data StreamHeapHard
- Find Motion PeriodsLinear ScanEasy
- 162. Find Peak ElementBinary SearchMedium
- 724. Find Pivot IndexPrefix SumEasy
- Find the Admin UserDAG TraversalMedium
- 997. Find the Town JudgeGraphEasy
- First Bad VersionBinary SearchEasy
- 41. First Missing PositiveArray ManipulationHard
- Fishing PondsGreedyMedium
- 733. Flood FillBFSEasy
- 904. Fruit Into BasketsSliding WindowMedium
- 134. Gas StationGreedyMedium
- 22. Generate ParenthesesBacktrackingMedium
- 824. Goat LatinString ManipulationEasy
- 49. Group AnagramsHash MapMedium
- 846. Hand of StraightsGreedyMedium
- 202. Happy NumberFast & Slow PointersEasy
- 213. House Robber IIDynamic ProgrammingMedium
- 232. Implement Queue using StacksStackEasy
- 380. Insert Delete GetRandom O(1)Hash Map + ArrayMedium
- 57. Insert IntervalArray ManipulationMedium
- 349. Intersection of Two ArraysHash MapEasy
- 160. Intersection of Two Linked ListsTwo PointersEasy
- Invert Binary TreeRecursionEasy
- 392. Is SubsequenceTwo PointersEasy
- 463. Island PerimeterMatrixEasy
- 205. Isomorphic StringsHash MapEasy
- JSON to CSV ConverterData transformation · recursive traversalMedium
- 1345. Jump Game IVBFSHard
- 973. K Closest Points to OriginHeapMedium
- Key-Value Store with TransactionsStackMedium
- 841. Keys and RoomsDFSMedium
- 703. Kth Largest Element in a StreamHeapEasy
- 1539. Kth Missing Positive NumberBinary SearchEasy
- 368. Largest Divisible SubsetDynamic ProgrammingMedium
- 84. Largest Rectangle in HistogramMonotonic StackHard
- Largest Tree in a ForestDFSEasy
- 1046. Last Stone WeightHeapEasy
- 17. Letter Combinations of a Phone NumberBacktrackingMedium
- 460. LFU CacheHash Map + Doubly Linked ListHard
- Linked List CycleFast and Slow PointersEasy
- 142. Linked List Cycle IIFast & Slow PointersMedium
- Log Query MatchingHash MapMedium
- 14. Longest Common PrefixString ManipulationEasy
- 128. Longest Consecutive SequenceHash MapMedium
- 329. Longest Increasing Path in a MatrixDFSHard
- 300. Longest Increasing SubsequenceDynamic ProgrammingMedium
- 3. Longest Substring Without Repeating CharactersSliding WindowMedium
- 32. Longest Valid ParenthesesStackHard
- 235. Lowest Common Ancestor of a Binary Search TreeDFSMedium
- 236. Lowest Common Ancestor of a Binary TreeDFSMedium
- 146. LRU CacheHash Map + Doubly Linked ListMedium
- Majority ElementBoyer-Moore VotingEasy
- 827. Making A Large IslandDFSHard
- 85. Maximal RectangleMonotonic StackHard
- Maximize Maximum Subarray Sum with K SwapsGreedy / Kadane's AlgorithmMedium
- 104. Maximum Depth of Binary TreeDFSEasy
- 895. Maximum Frequency StackStackHard
- Maximum of Window MinimumsSliding WindowMedium
- 1235. Maximum Profit in Job SchedulingDynamic ProgrammingHard
- 325. Maximum Size Subarray Sum Equals kPrefix SumMedium
- Maximum Stone CollectionDynamic ProgrammingMedium
- 918. Maximum Sum Circular SubarrayKadane's AlgorithmMedium
- Maximum Valid Matrix ExpressionMatrix TraversalMedium
- 4. Median of Two Sorted ArraysBinary SearchHard
- 253. Meeting Rooms IIHeapMedium
- 56. Merge IntervalsArray ManipulationMedium
- 23. Merge k Sorted ListsHeapHard
- 88. Merge Sorted ArrayTwo PointersEasy
- 1768. Merge Strings AlternatelyTwo PointersEasy
- 617. Merge Two Binary TreesDFSEasy
- 21. Merge Two Sorted ListsLinked List ManipulationEasy
- Merged Shift TimelineSweep LineMedium
- 876. Middle of the Linked ListFast & Slow PointersEasy
- 746. Min Cost Climbing StairsDynamic ProgrammingEasy
- 155. Min StackStackEasy
- 530. Minimum Absolute Difference in BSTDFSEasy
- 921. Minimum Add to Make Parentheses ValidStackMedium
- 939. Minimum Area RectangleHash MapMedium
- Minimum Coins with Limited InventoryBounded KnapsackHard
- 2260. Minimum Consecutive Cards to Pick UpHash MapMedium
- Minimum Cut to Disconnect LeavesDFSMedium
- Minimum Deletions to Cap Tree HeightDFSHard
- Minimum Repaints for K Black CellsSliding WindowEasy
- Minimum Swaps to Group EvensSliding WindowMedium
- 1443. Minimum Time to Collect All Apples in a TreeDFSMedium
- 76. Minimum Window SubstringSliding WindowHard
- 268. Missing NumberArray ManipulationEasy
- Molecular WeightStackMedium
- 283. Move ZeroesTwo PointersEasy
- 346. Moving Average from Data StreamSliding WindowEasy
- 51. N-QueensBacktrackingHard
- 743. Network Delay TimeDijkstra'sMedium
- 496. Next Greater Element IMonotonic StackEasy
- 31. Next PermutationArray ManipulationMedium
- 1155. Number of Dice Rolls With Target SumDynamic ProgrammingMedium
- 200. Number of IslandsDFSMedium
- 305. Number of Islands IIUnion FindHard
- 547. Number of ProvincesUnion FindMedium
- 1944. Number of Visible People in a QueueMonotonic StackHard
- 1639. Number of Ways to Form a Target String Given a DictionaryDynamic ProgrammingHard
- 465. Optimal Account BalancingBacktrackingHard
- 417. Pacific Atlantic Water FlowDFSMedium
- 1010. Pairs of Songs With Total Durations Divisible by 60Hash MapMedium
- 234. Palindrome Linked ListFast & Slow PointersEasy
- 86. Partition ListLinked List ManipulationMedium
- 118. Pascal's TriangleDynamic ProgrammingEasy
- 112. Path SumDFSEasy
- 1219. Path with Maximum GoldBacktrackingMedium
- 46. PermutationsBacktrackingMedium
- 238. Product of Array Except SelfPrefix SumMedium
- Profiler Samples to TraceStackMedium
- 528. Random Pick with WeightBinary SearchMedium
- 303. Range Sum Query - ImmutablePrefix SumEasy
- 10. Regular Expression MatchingDynamic ProgrammingHard
- 83. Remove Duplicates from Sorted ListLinked List ManipulationEasy
- 301. Remove Invalid ParenthesesBacktrackingHard
- 1962. Remove Stones to Minimize the TotalHeapMedium
- 143. Reorder ListLinked List ManipulationMedium
- Resilient Graph APIUnreliable dependencies · retries · graph searchHard
- 206. Reverse Linked ListLinked List ManipulationEasy
- 25. Reverse Nodes in k-GroupLinked List ManipulationHard
- 151. Reverse Words in a StringString ManipulationMedium
- 13. Roman to IntegerString ManipulationEasy
- 48. Rotate ImageMatrixMedium
- 994. Rotting OrangesBFSMedium
- Run-Length DecodingString ManipulationEasy
- 100. Same TreeDFSEasy
- Scattered Palindrome SubstringsBit ManipulationMedium
- 87. Scramble StringDynamic ProgrammingHard
- 74. Search a 2D MatrixBinary SearchMedium
- 33. Search in Rotated Sorted ArrayBinary SearchMedium
- 35. Search Insert PositionBinary SearchEasy
- 1268. Search Suggestions SystemTrieMedium
- 297. Serialize and Deserialize Binary TreeTree SerializationHard
- 428. Serialize and Deserialize N-ary TreeTree SerializationHard
- SET Card GameHash MapMedium
- 317. Shortest Distance from All BuildingsBFSHard
- 1293. Shortest Path in a Grid with Obstacles EliminationBFSHard
- 1091. Shortest Path in Binary MatrixBFSMedium
- 862. Shortest Subarray with Sum at Least KMonotonic StackHard
- Simple SQL SELECT EngineParsing · expression evaluationHard
- 239. Sliding Window MaximumSliding WindowHard
- Sliding Window Rate LimiterSliding WindowEasy
- 75. Sort ColorsTwo PointersMedium
- 54. Spiral MatrixMatrixMedium
- 410. Split Array Largest SumBinary SearchHard
- String Overlap MergeString ManipulationEasy
- Subarray Sum Equals KPrefix Sum + Hash MapMedium
- 992. Subarrays with K Different IntegersSliding WindowHard
- 572. Subtree of Another TreeDFSEasy
- 37. Sudoku SolverBacktrackingHard
- 404. Sum of Left LeavesDFSEasy
- 129. Sum Root to Leaf NumbersDFSMedium
- 228. Summary RangesArray ManipulationEasy
- 778. Swim in Rising WaterDijkstra'sHard
- 101. Symmetric TreeDFSEasy
- 68. Text JustificationString ManipulationHard
- 1101. The Earliest Moment When Everyone Become FriendsUnion FindMedium
- 505. The Maze IIDijkstra'sMedium
- 218. The Skyline ProblemHeapHard
- Tic Tac Tree WinnerMatrix TraversalEasy
- Tic-Tac-Toe with K in a RowMatrixMedium
- 981. Time Based Key-Value StoreHash Map + Binary SearchMedium
- 1376. Time Needed to Inform All EmployeesDFSMedium
- 347. Top K Frequent ElementsHeapMedium
- 692. Top K Frequent WordsHeapMedium
- Transactional Key-Value StoreStateful services · layered stateMedium
- 42. Trapping Rain WaterTwo PointersHard
- 1. Two SumHash MapEasy
- 167. Two Sum II - Input Array Is SortedTwo PointersEasy
- Two Sum with Best Pair Under TargetTwo PointersEasy
- 96. Unique Binary Search TreesDynamic ProgrammingMedium
- 62. Unique PathsDynamic ProgrammingMedium
- 980. Unique Paths IIIBacktrackingHard
- 242. Valid AnagramHash MapEasy
- 125. Valid PalindromeTwo PointersEasy
- 680. Valid Palindrome IITwo PointersEasy
- 20. Valid ParenthesesStackEasy
- 36. Valid SudokuMatrixMedium
- 408. Valid Word AbbreviationString ManipulationEasy
- 98. Validate Binary Search TreeDFSMedium
- 1361. Validate Binary Tree NodesGraphMedium
- Verify Permutation In-PlaceCyclic SortMedium
- 286. Walls and GatesBFSMedium
- Web Crawler Same HostBreadth-First SearchMedium
- 44. Wildcard MatchingDynamic ProgrammingHard
- 139. Word BreakDynamic ProgrammingMedium
- Word LadderBreadth-First SearchHard
- 212. Word Search IITrieHard