Problems

440 題。用下方條件即時篩選。要搜解法內文請用 🔍 全文搜尋。

🗂️ Arrays & Hashing#1Two SumEasy★★★★★⏱ O(n)

🔗 Linked List#2Add Two NumbersMedium★★★★★⏱ O(max(n, m))

🪟 Sliding Window#3Longest Substring Without Repeating CharactersMedium★★★★★⏱ O(n)

🔍 Binary Search#4Median of Two Sorted ArraysHard★★★★★⏱ O(log(min(m, n)))

📈 1-D DP#5Longest Palindromic SubstringMedium★★★★★⏱ O(n^2)

📐 Math & Geometry#6Zigzag ConversionMedium★★★★★⏱ O(n)

🔢 Bit Manipulation#7Reverse IntegerMedium★★★★★⏱ O(log x)

📐 Math & Geometry#8String to Integer (atoi)Medium★★★★★⏱ O(n)

📐 Math & Geometry#9Palindrome NumberEasy★★★★★⏱ O(log n)

🧮 2-D DP#10Regular Expression MatchingHard★★★★★⏱ O(m * n)

👉 Two Pointers#11Container With Most WaterMedium★★★★★⏱ O(n)

📐 Math & Geometry#12Integer to RomanMedium★★★★★⏱ O(1)

📐 Math & Geometry#13Roman to IntegerEasy★★★★★⏱ O(n)

🗂️ Arrays & Hashing#14Longest Common PrefixEasy★★★★★⏱ O(S)

👉 Two Pointers#153SumMedium★★★★★⏱ O(n^2)

🔙 Backtracking#17Letter Combinations of a Phone NumberMedium★★★★★⏱ O(4^n * n)

👉 Two Pointers#184SumMedium★★★★★⏱ O(n³)

🔗 Linked List#19Remove Nth Node From End of ListMedium★★★★★⏱ O(n)

📚 Stack#20Valid ParenthesesEasy★★★★★⏱ O(n)

🔗 Linked List#21Merge Two Sorted ListsEasy★★★★★⏱ O(n + m)

📚 Stack#22Generate ParenthesesMedium★★★★★

🔗 Linked List#23Merge k Sorted ListsHard★★★★★⏱ O(N log k)

🔗 Linked List#24Swap Nodes In PairsMedium★★★★★⏱ O(n)

🔗 Linked List#25Reverse Nodes in k-GroupHard★★★★★⏱ O(n)

👉 Two Pointers#26Remove Duplicates From Sorted ArrayEasy★★★★★⏱ O(n)

🗂️ Arrays & Hashing#27Remove ElementEasy★★★★★⏱ O(n)

🗂️ Arrays & Hashing#28Find The Index of The First Occurrence in a StringEasy★★★★★⏱ O(n + m)

🔢 Bit Manipulation#29Divide Two IntegersMedium★★★★★⏱ O(log²n)

🗂️ Arrays & Hashing#31Next PermutationMedium★★★★★⏱ O(n)

📚 Stack#32Longest Valid ParenthesesHard★★★★★⏱ O(n)

🔍 Binary Search#33Search in Rotated Sorted ArrayMedium★★★★★⏱ O(log n)

🔍 Binary Search#34Find First and Last Position of Element in Sorted ArrayMedium★★★★★⏱ O(log n)

🔍 Binary Search#35Search Insert PositionEasy★★★★★⏱ O(log n)

🗂️ Arrays & Hashing#36Valid SudokuMedium★★★★★⏱ O(1)

🔙 Backtracking#39Combination SumMedium★★★★★

🔙 Backtracking#40Combination Sum IIMedium★★★★★⏱ O(2^n)

🗂️ Arrays & Hashing#41First Missing PositiveHard★★★★★⏱ O(n)

👉 Two Pointers#42Trapping Rain WaterHard★★★★★⏱ O(n)

📐 Math & Geometry#43Multiply StringsMedium★★★★★⏱ O(m * n)

🧮 2-D DP#44Wildcard MatchingHard★★★★★⏱ O(m·n)

🪙 Greedy#45Jump Game IIMedium★★★★★⏱ O(n)

🔙 Backtracking#46PermutationsMedium★★★★★⏱ O(n * n!)

🔙 Backtracking#47Permutations IIMedium★★★★★⏱ O(n! * n)

📐 Math & Geometry#48Rotate ImageMedium★★★★★⏱ O(n^2)

🗂️ Arrays & Hashing#49Group AnagramsMedium★★★★★⏱ O(n * k)

📐 Math & Geometry#50Pow(x, n)Medium★★★★★⏱ O(log n)

🔙 Backtracking#51N-QueensHard★★★★★⏱ O(n!)

🔙 Backtracking#52N Queens IIHard★★★★★⏱ O(n!)

🪙 Greedy#53Maximum SubarrayMedium★★★★★⏱ O(n)

📐 Math & Geometry#54Spiral MatrixMedium★★★★★⏱ O(m * n)

🪙 Greedy#55Jump GameMedium★★★★★⏱ O(n)

📏 Intervals#56Merge IntervalsMedium★★★★★⏱ O(n log n)

📏 Intervals#57Insert IntervalMedium★★★★★⏱ O(n)

🗂️ Arrays & Hashing#58Length of Last WordEasy★★★★★⏱ O(n)

📐 Math & Geometry#59Spiral Matrix IIMedium★★★★★⏱ O(n^2)

🔗 Linked List#61Rotate ListMedium★★★★★⏱ O(n)

🧮 2-D DP#62Unique PathsMedium★★★★★⏱ O(m * n)

🧮 2-D DP#63Unique Paths IIMedium★★★★★⏱ O(m * n)

🧮 2-D DP#64Minimum Path SumMedium★★★★★⏱ O(m * n)

📐 Math & Geometry#66Plus OneEasy★★★★★⏱ O(n)

🔢 Bit Manipulation#67Add BinaryEasy★★★★★⏱ O(max(m, n))

🗂️ Arrays & Hashing#68Text JustificationHard★★★★★⏱ O(n * maxWidth)

🔍 Binary Search#69Sqrt(x)Easy★★★★★⏱ O(log x)

📈 1-D DP#70Climbing StairsEasy★★★★★⏱ O(n)

📚 Stack#71Simplify PathMedium★★★★★⏱ O(n)

🧮 2-D DP#72Edit DistanceMedium★★★★★⏱ O(m * n)

📐 Math & Geometry#73Set Matrix ZeroesMedium★★★★★⏱ O(m * n)

🔍 Binary Search#74Search a 2D MatrixMedium★★★★★⏱ O(log(m * n))

🗂️ Arrays & Hashing#75Sort ColorsMedium★★★★★⏱ O(n)

🪟 Sliding Window#76Minimum Window SubstringHard★★★★★⏱ O(n)

🔙 Backtracking#77CombinationsMedium★★★★★⏱ O(C(n,k) * k)

🔙 Backtracking#78SubsetsMedium★★★★★⏱ O(n * 2^n)

🔙 Backtracking#79Word SearchMedium★★★★★⏱ O(m * n * 4^L)

👉 Two Pointers#80Remove Duplicates From Sorted Array IIMedium★★★★★⏱ O(n)

🔍 Binary Search#81Search In Rotated Sorted Array IIMedium★★★★★⏱ O(log n)

🔗 Linked List#83Remove Duplicates From Sorted ListEasy★★★★★⏱ O(n)

📚 Stack#84Largest Rectangle in HistogramHard★★★★★⏱ O(n)

📚 Stack#85Maximal RectangleHard★★★★★⏱ O(m·n)

🔗 Linked List#86Partition ListMedium★★★★★⏱ O(n)

👉 Two Pointers#88Merge Sorted ArrayEasy★★★★★⏱ O(m + n)

🔙 Backtracking#90Subsets IIMedium★★★★★⏱ O(n * 2^n)

📈 1-D DP#91Decode WaysMedium★★★★★⏱ O(n)

🔗 Linked List#92Reverse Linked List IIMedium★★★★★⏱ O(n)

🔙 Backtracking#93Restore IP AddressesMedium★★★★★⏱ O(3^4)

🌳 Trees#94Binary Tree Inorder TraversalEasy★★★★★⏱ O(n)

🌳 Trees#95Unique Binary Search Trees IIMedium★★★★★⏱ O(n * C(n))

🌳 Trees#96Unique Binary Search TreesMedium★★★★★⏱ O(n)

🧮 2-D DP#97Interleaving StringMedium★★★★★⏱ O(m * n)

🌳 Trees#98Validate Binary Search TreeMedium★★★★★⏱ O(n)

🌳 Trees#100Same TreeEasy★★★★★⏱ O(n)

🌳 Trees#101Symmetric TreeEasy★★★★★⏱ O(n)

🌳 Trees#102Binary Tree Level Order TraversalMedium★★★★★⏱ O(n)

🌳 Trees#103Binary Tree Zigzag Level Order TraversalMedium★★★★★⏱ O(n)

🌳 Trees#104Maximum Depth of Binary TreeEasy★★★★★⏱ O(n)

🌳 Trees#105Construct Binary Tree from Preorder and Inorder TraversalMedium★★★★★⏱ O(n)

🌳 Trees#106Construct Binary Tree from Inorder and Postorder TraversalMedium★★★★★⏱ O(n)

🌳 Trees#108Convert Sorted Array to Binary Search TreeEasy★★★★★⏱ O(n)

🌳 Trees#110Balanced Binary TreeEasy★★★★★⏱ O(n)

🌳 Trees#112Path SumEasy★★★★★⏱ O(n)

🧮 2-D DP#115Distinct SubsequencesHard★★★★★⏱ O(m * n)

🔍 Binary Search#116Populating Next Right Pointers in Each NodeMedium★★★★★⏱ O(n)

🗂️ Arrays & Hashing#118Pascals TriangleEasy★★★★★⏱ O(numRows^2)

📈 1-D DP#120TriangleMedium★★★★★⏱ O(n^2)

🪟 Sliding Window#121Best Time to Buy and Sell StockEasy★★★★★⏱ O(n)

🗂️ Arrays & Hashing#122Best Time to Buy And Sell Stock IIMedium★★★★★⏱ O(n)

🧮 2-D DP#123Best Time to Buy and Sell Stock IIIHard★★★★★⏱ O(n)

🌳 Trees#124Binary Tree Maximum Path SumHard★★★★★⏱ O(n)

👉 Two Pointers#125Valid PalindromeEasy★★★★★⏱ O(n)

🗺️ Graphs#126Word Ladder IIHard★★★★★⏱ O(N·L·26)

🗺️ Graphs#127Word LadderHard★★★★★⏱ O(m^2 * n)

🗂️ Arrays & Hashing#128Longest Consecutive SequenceMedium★★★★★⏱ O(n)

🌳 Trees#129Sum Root to Leaf NumbersMedium★★★★★⏱ O(n)

🗺️ Graphs#130Surrounded RegionsMedium★★★★★⏱ O(m * n)

🔙 Backtracking#131Palindrome PartitioningMedium★★★★★⏱ O(n^2 + 2^n)

🗺️ Graphs#133Clone GraphMedium★★★★★⏱ O(V + E)

🪙 Greedy#134Gas StationMedium★★★★★⏱ O(n)

🪙 Greedy#135CandyHard★★★★★⏱ O(n)

🔢 Bit Manipulation#136Single NumberEasy★★★★★⏱ O(n)

🔗 Linked List#138Copy List with Random PointerMedium★★★★★⏱ O(n)

📈 1-D DP#139Word BreakMedium★★★★★⏱ O(n^2 * m)

🔙 Backtracking#140Word Break IIHard★★★★★⏱ O(n² + total output)

🔗 Linked List#141Linked List CycleEasy★★★★★⏱ O(n)

🔗 Linked List#143Reorder ListMedium★★★★★⏱ O(n)

🌳 Trees#144Binary Tree Preorder TraversalEasy★★★★★⏱ O(n)

🌳 Trees#145Binary Tree Postorder TraversalEasy★★★★★⏱ O(n)

🔗 Linked List#146LRU CacheMedium★★★★★⏱ O(1)

🔗 Linked List#147Insertion Sort ListMedium★★★★★⏱ O(n^2)

🔗 Linked List#148Sort ListMedium★★★★★⏱ O(n log n)

📐 Math & Geometry#149Max Points on a LineHard★★★★★⏱ O(n^2)

📚 Stack#150Evaluate Reverse Polish NotationMedium★★★★★⏱ O(n)

📈 1-D DP#152Maximum Product SubarrayMedium★★★★★⏱ O(n)

🔍 Binary Search#153Find Minimum in Rotated Sorted ArrayMedium★★★★★⏱ O(log n)

📚 Stack#155Min StackMedium★★★★★⏱ O(1)

🔗 Linked List#160Intersection of Two Linked ListsEasy★★★★★⏱ O(m + n)

🔍 Binary Search#162Find Peak ElementMedium★★★★★⏱ O(log n)

👉 Two Pointers#167Two Sum II - Input Array Is SortedMedium★★★★★⏱ O(n)

📐 Math & Geometry#168Excel Sheet Column TitleEasy★★★★★⏱ O(log26 n)

🗂️ Arrays & Hashing#169Majority ElementEasy★★★★★⏱ O(n)

🌳 Trees#173Binary Search Tree IteratorMedium★★★★★⏱ O(1)

🧮 2-D DP#174Dungeon GameHard★★★★★⏱ O(m·n)

🗂️ Arrays & Hashing#179Largest NumberMedium★★★★★⏱ O(n log n * k)

🗂️ Arrays & Hashing#187Repeated DNA SequencesMedium★★★★★⏱ O(n)

🧮 2-D DP#188Best Time to Buy and Sell Stock IVHard★★★★★⏱ O(n·k)

👉 Two Pointers#189Rotate ArrayMedium★★★★★⏱ O(n)

🔢 Bit Manipulation#190Reverse BitsEasy★★★★★⏱ O(1)

🔢 Bit Manipulation#191Number of 1 BitsEasy★★★★★⏱ O(k)

📈 1-D DP#198House RobberMedium★★★★★⏱ O(n)

🌳 Trees#199Binary Tree Right Side ViewMedium★★★★★⏱ O(n)

🗺️ Graphs#200Number of IslandsMedium★★★★★⏱ O(m * n)

📐 Math & Geometry#202Happy NumberEasy★★★★★⏱ O(log n)

🔗 Linked List#203Remove Linked List ElementsEasy★★★★★⏱ O(n)

🗂️ Arrays & Hashing#205Isomorphic StringsEasy★★★★★⏱ O(n^2)

🔗 Linked List#206Reverse Linked ListEasy★★★★★⏱ O(n)

🗺️ Graphs#207Course ScheduleMedium★★★★★⏱ O(V + E)

🌲 Tries#208Implement Trie (Prefix Tree)Medium★★★★★⏱ O(m)

🪟 Sliding Window#209Minimum Size Subarray SumMedium★★★★★⏱ O(n)

🗺️ Graphs#210Course Schedule IIMedium★★★★★⏱ O(V + E)

🌲 Tries#211Design Add and Search Words Data StructureMedium★★★★★⏱ O(m)

🌲 Tries#212Word Search IIHard★★★★★⏱ O(M * N * 4^L)

📈 1-D DP#213House Robber IIMedium★★★★★⏱ O(n)

⛰️ Heap / Priority Queue#215Kth Largest Element in an ArrayMedium★★★★★⏱ O(n)

🗂️ Arrays & Hashing#217Contains DuplicateEasy★★★★★⏱ O(n)

⛰️ Heap / Priority Queue#218The Skyline ProblemHard★★★★★⏱ O(n log n)

🪟 Sliding Window#219Contains Duplicate IIEasy★★★★★⏱ O(n)

🧮 2-D DP#221Maximal SquareMedium★★★★★⏱ O(m * n)

📚 Stack#225Implement Stack Using QueuesEasy★★★★★⏱ O(n)

🌳 Trees#226Invert Binary TreeEasy★★★★★⏱ O(n)

📚 Stack#227Basic Calculator IIMedium★★★★★⏱ O(n)

🌳 Trees#230Kth Smallest Element in a BSTMedium★★★★★⏱ O(h + k)

🔗 Linked List#234Palindrome Linked ListEasy★★★★★⏱ O(n)

🌳 Trees#235Lowest Common Ancestor of a Binary Search TreeMedium★★★★★⏱ O(h)

🌳 Trees#236Lowest Common Ancestor of a Binary TreeMedium★★★★★⏱ O(n)

🗂️ Arrays & Hashing#238Product of Array Except SelfMedium★★★★★⏱ O(n)

🪟 Sliding Window#239Sliding Window MaximumHard★★★★★⏱ O(n)

🔍 Binary Search#240Search a 2D Matrix IIMedium★★★★★⏱ O(m + n)

🗂️ Arrays & Hashing#242Valid AnagramEasy★★★★★⏱ O(n)

📏 Intervals#252Meeting RoomsEasy★★★★★⏱ O(n log n)

📏 Intervals#253Meeting Rooms IIMedium★★★★★⏱ O(n log n)

📈 1-D DP#256Paint HouseMedium★★★★★⏱ O(n)

🗺️ Graphs#261Graph Valid TreeMedium★★★★★⏱ O(E * α(n))

📐 Math & Geometry#263Ugly NumberEasy★★★★★⏱ O(log n)

🔢 Bit Manipulation#268Missing NumberEasy★★★★★⏱ O(n)

🕸️ Advanced Graphs#269Alien DictionaryHard★★★★★⏱ O(C)

🗂️ Arrays & Hashing#271Encode and Decode StringsMedium★★★★★⏱ O(n)

📈 1-D DP#279Perfect SquaresMedium★★★★★⏱ O(n * sqrt(n))

🗂️ Arrays & Hashing#280Wiggle SortMedium★★★★★⏱ O(n)

👉 Two Pointers#283Move ZeroesEasy★★★★★⏱ O(n)

🗺️ Graphs#286Walls and GatesMedium★★★★★⏱ O(m * n)

🔗 Linked List#287Find the Duplicate NumberMedium★★★★★⏱ O(n)

🗂️ Arrays & Hashing#290Word PatternEasy★★★★★⏱ O(n)

⛰️ Heap / Priority Queue#295Find Median from Data StreamHard★★★★★⏱ O(log n)

🌳 Trees#297Serialize and Deserialize Binary TreeHard★★★★★⏱ O(n)

📈 1-D DP#300Longest Increasing SubsequenceMedium★★★★★⏱ O(n log n)

🗂️ Arrays & Hashing#303Range Sum Query - ImmutableEasy★★★★★⏱ O(n)

🗂️ Arrays & Hashing#304Range Sum Query 2D ImmutableMedium★★★★★⏱ O(m*n)

🗂️ Arrays & Hashing#307Range Sum Query - MutableMedium★★★★★⏱ O(log n)

🧮 2-D DP#309Best Time to Buy and Sell Stock with CooldownMedium★★★★★⏱ O(n)

🧮 2-D DP#312Burst BalloonsHard★★★★★⏱ O(n^3)

🔍 Binary Search#315Count of Smaller Numbers After SelfHard★★★★★⏱ O(n log n)

📚 Stack#316Remove Duplicate LettersMedium★★★★★⏱ O(n)

📈 1-D DP#322Coin ChangeMedium★★★★★⏱ O(amount * coins.size)

🗺️ Graphs#323Number of Connected Components in an Undirected GraphMedium★★★★★⏱ O(E * α(n))

🧮 2-D DP#329Longest Increasing Path in a MatrixHard★★★★★⏱ O(m * n)

🕸️ Advanced Graphs#332Reconstruct ItineraryHard★★★★★⏱ O(E log E)

🌳 Trees#337House Robber IIIMedium★★★★★⏱ O(n)

🔢 Bit Manipulation#338Counting BitsEasy★★★★★⏱ O(n)

📈 1-D DP#343Integer BreakMedium★★★★★⏱ O(1)

👉 Two Pointers#344Reverse StringEasy★★★★★⏱ O(n)

🗂️ Arrays & Hashing#347Top K Frequent ElementsMedium★★★★★⏱ O(n)

📏 Intervals#352Data Stream as Disjoint IntervalsHard★★★★★⏱ O(log n)

📈 1-D DP#354Russian Doll EnvelopesHard★★★★★⏱ O(n log n)

⛰️ Heap / Priority Queue#355Design TwitterMedium★★★★★⏱ O(k log k)

🔍 Binary Search#367Valid Perfect SquareEasy★★★★★⏱ O(log n)

🔢 Bit Manipulation#371Sum of Two IntegersMedium★★★★★⏱ O(32)

🔍 Binary Search#374Guess Number Higher Or LowerEasy★★★★★⏱ O(log n)

📈 1-D DP#377Combination Sum IVMedium★★★★★⏱ O(target * n)

🗂️ Arrays & Hashing#380Insert Delete Get Random O(1)Medium★★★★★⏱ O(1)

🗂️ Arrays & Hashing#392Is SubsequenceEasy★★★★★⏱ O(n)

📚 Stack#394Decode StringMedium★★★★★⏱ O(n * maxK)

🗺️ Graphs#399Evaluate DivisionMedium★★★★★⏱ O(Q * (V + E))

📚 Stack#402Remove K DigitsMedium★★★★★⏱ O(n)

🔍 Binary Search#410Split Array Largest SumHard★★★★★⏱ O(n * log(sum(nums)))

📈 1-D DP#416Partition Equal Subset SumMedium★★★★★⏱ O(n * target)

🗺️ Graphs#417Pacific Atlantic Water FlowMedium★★★★★⏱ O(m * n)

🪟 Sliding Window#424Longest Repeating Character ReplacementMedium★★★★★⏱ O(n)

🌳 Trees#427Construct Quad TreeMedium★★★★★⏱ O(n^2 log n)

📏 Intervals#435Non-overlapping IntervalsMedium★★★★★⏱ O(n log n)

🗂️ Arrays & Hashing#438Find All Anagrams in a StringMedium★★★★★⏱ O(n)

🔍 Binary Search#441Arranging CoinsEasy★★★★★⏱ O(log n)

🗂️ Arrays & Hashing#448Find All Numbers Disappeared in An ArrayEasy★★★★★⏱ O(n)

🌳 Trees#450Delete Node in a BSTMedium★★★★★⏱ O(h)

📚 Stack#456132 PatternMedium★★★★★⏱ O(n)

🔗 Linked List#460LFU CacheHard★★★★★⏱ O(1)

🗺️ Graphs#463Island PerimeterEasy★★★★★⏱ O(m * n)

📈 1-D DP#472Concatenated WordsHard★★★★★⏱ O(n * L^2)

🔙 Backtracking#473Matchsticks to SquareMedium★★★★★⏱ O(4^n)

🧮 2-D DP#474Ones and ZeroesMedium★★★★★⏱ O(k * m * n)

🧮 2-D DP#494Target SumMedium★★★★★⏱ O(n * target)

🗂️ Arrays & Hashing#496Next Greater Element IEasy★★★★★⏱ O(n + m)

⛰️ Heap / Priority Queue#502IPOHard★★★★★⏱ O(n log n)

🌳 Trees#513Find Bottom Left Tree ValueMedium★★★★★⏱ O(n)

🧮 2-D DP#516Longest Palindromic SubsequenceMedium★★★★★⏱ O(n^2)

🧮 2-D DP#518Coin Change IIMedium★★★★★⏱ O(n * amount)

🗂️ Arrays & Hashing#523Continuous Subarray SumMedium★★★★★⏱ O(n)

🔍 Binary Search#528Random Pick with WeightMedium★★★★★⏱ O(n)

🗂️ Arrays & Hashing#535Encode and Decode TinyURLMedium★★★★★⏱ O(1)

🌳 Trees#538Convert BST to Greater TreeMedium★★★★★⏱ O(n)

🔍 Binary Search#540Single Element in a Sorted ArrayMedium★★★★★⏱ O(log n)

🌳 Trees#543Diameter of Binary TreeEasy★★★★★⏱ O(n)

🗂️ Arrays & Hashing#554Brick WallMedium★★★★★⏱ O(n * m)

🗂️ Arrays & Hashing#560Subarray Sum Equals KMedium★★★★★⏱ O(n)

🪟 Sliding Window#567Permutation in StringMedium★★★★★⏱ O(n)

🌳 Trees#572Subtree of Another TreeEasy★★★★★⏱ O(m * n)

🗂️ Arrays & Hashing#605Can Place FlowersEasy★★★★★⏱ O(n)

🌳 Trees#606Construct String From Binary TreeEasy★★★★★⏱ O(n)

🌳 Trees#617Merge Two Binary TreesEasy★★★★★⏱ O(min(m, n))

⛰️ Heap / Priority Queue#621Task SchedulerMedium★★★★★⏱ O(m * n)

🔗 Linked List#622Design Circular QueueMedium★★★★★⏱ O(1)

🪙 Greedy#646Maximum Length of Pair ChainMedium★★★★★⏱ O(n log n)

📈 1-D DP#647Palindromic SubstringsMedium★★★★★⏱ O(n^2)

🪙 Greedy#649Dota2 SenateMedium★★★★★⏱ O(n)

🌳 Trees#652Find Duplicate SubtreesMedium★★★★★⏱ O(n)

🪟 Sliding Window#658Find K Closest ElementsMedium★★★★★⏱ O(log(n-k) + k)

🌳 Trees#662Maximum Width of Binary TreeMedium★★★★★⏱ O(n)

🗂️ Arrays & Hashing#665Non Decreasing ArrayMedium★★★★★⏱ O(n)

🌳 Trees#669Trim a Binary Search TreeMedium★★★★★⏱ O(n)

📈 1-D DP#673Number of Longest Increasing SubsequenceMedium★★★★★⏱ O(n log n)

🪙 Greedy#678Valid Parenthesis StringMedium★★★★★⏱ O(n)

👉 Two Pointers#680Valid Palindrome IIEasy★★★★★⏱ O(n)

📚 Stack#682Baseball GameEasy★★★★★⏱ O(n)

🗺️ Graphs#684Redundant ConnectionMedium★★★★★⏱ O(n * α(n))

📈 1-D DP#691Stickers to Spell WordHard★★★★★⏱ O(2^n * m * n)

🗺️ Graphs#695Max Area of IslandMedium★★★★★⏱ O(m * n)

🔙 Backtracking#698Partition to K Equal Sum SubsetsMedium★★★★★⏱ O(n * 2^n)

🌳 Trees#701Insert into a Binary Search TreeMedium★★★★★⏱ O(h)

⛰️ Heap / Priority Queue#703Kth Largest Element in a StreamEasy★★★★★⏱ O(log k)

🔍 Binary Search#704Binary SearchEasy★★★★★⏱ O(log n)

🗂️ Arrays & Hashing#705Design HashSetEasy★★★★★⏱ O(1)

🗂️ Arrays & Hashing#706Design HashMapEasy★★★★★⏱ O(1)

🔗 Linked List#707Design Linked ListMedium★★★★★⏱ O(n)

🗺️ Graphs#721Accounts MergeMedium★★★★★⏱ O(N * K * α(N * K))

🗂️ Arrays & Hashing#724Find Pivot IndexEasy★★★★★⏱ O(n)

🔗 Linked List#725Split Linked List in PartsMedium★★★★★⏱ O(n + k)

📚 Stack#735Asteroid CollisionMedium★★★★★⏱ O(n)

📚 Stack#739Daily TemperaturesMedium★★★★★⏱ O(n)

📈 1-D DP#740Delete And EarnMedium★★★★★⏱ O(n + maxVal)

🕸️ Advanced Graphs#743Network Delay TimeMedium★★★★★⏱ O(E log V)

📈 1-D DP#746Min Cost Climbing StairsEasy★★★★★⏱ O(n)

🗺️ Graphs#752Open The LockMedium★★★★★⏱ O(10^4 * 4)

🪙 Greedy#763Partition LabelsMedium★★★★★⏱ O(n)

⛰️ Heap / Priority Queue#767Reorganize StringMedium★★★★★⏱ O(n log 26)

🕸️ Advanced Graphs#778Swim in Rising WaterHard★★★★★⏱ O(n^2 log n)

🌳 Trees#783Minimum Distance Between BST NodesEasy★★★★★⏱ O(n)

🗺️ Graphs#785Is Graph Bipartite?Medium★★★★★⏱ O(V + E)

🕸️ Advanced Graphs#787Cheapest Flights Within K StopsMedium★★★★★⏱ O(K * E)

🗺️ Graphs#802Find Eventual Safe StatesMedium★★★★★⏱ O(V + E)

📈 1-D DP#837New 21 GameMedium★★★★★⏱ O(k + maxPts)

🗂️ Arrays & Hashing#838Push DominoesMedium★★★★★⏱ O(n)

🪙 Greedy#846Hand of StraightsMedium★★★★★⏱ O(n log n)

📚 Stack#853Car FleetMedium★★★★★⏱ O(n log n)

🔍 Binary Search#875Koko Eating BananasMedium★★★★★⏱ O(n * log(max(piles)))

🔗 Linked List#876Middle of the Linked ListEasy★★★★★⏱ O(n)

🧮 2-D DP#877Stone GameMedium★★★★★⏱ O(1)

🧮 2-D DP#879Profitable SchemesHard★★★★★⏱ O(plans * n * minProfit)

👉 Two Pointers#881Boats to Save PeopleMedium★★★★★⏱ O(n log n)

🌳 Trees#894All Possible Full Binary TreesMedium★★★★★

📚 Stack#895Maximum Frequency StackHard★★★★★⏱ O(1)

📚 Stack#901Online Stock SpanMedium★★★★★⏱ O(1)

🪟 Sliding Window#904Fruit Into BasketsMedium★★★★★⏱ O(n)

🗺️ Graphs#909Snakes And LaddersMedium★★★★★⏱ O(n^2)

🗂️ Arrays & Hashing#912Sort an ArrayMedium★★★★★⏱ O(n log n)

🪙 Greedy#918Maximum Sum Circular SubarrayMedium★★★★★⏱ O(n)

🧮 2-D DP#920Number of Music PlaylistsHard★★★★★⏱ O(goal * n)

🧮 2-D DP#926Flip String to Monotone IncreasingMedium★★★★★⏱ O(n)

🗂️ Arrays & Hashing#929Unique Email AddressesEasy★★★★★⏱ O(n * m)

🗺️ Graphs#934Shortest BridgeMedium★★★★★⏱ O(n^2)

📚 Stack#946Validate Stack SequencesMedium★★★★★⏱ O(n)

🌳 Trees#951Flip Equivalent Binary TreesMedium★★★★★⏱ O(n)

🗺️ Graphs#953Verifying An Alien DictionaryEasy★★★★★⏱ O(n * m)

🌳 Trees#958Check Completeness of a Binary TreeMedium★★★★★⏱ O(n)

⛰️ Heap / Priority Queue#973K Closest Points to OriginMedium★★★★★⏱ O(n log k)

🔍 Binary Search#977Squares of a Sorted ArrayEasy★★★★★⏱ O(n)

🪙 Greedy#978Longest Turbulent SubarrayMedium★★★★★⏱ O(n)

🔍 Binary Search#981Time Based Key-Value StoreMedium★★★★★

📈 1-D DP#983Minimum Cost For TicketsMedium★★★★★⏱ O(maxDay)

🔢 Bit Manipulation#989Add to Array-Form of IntegerEasy★★★★★⏱ O(max(n, log k))

🗺️ Graphs#994Rotting OrangesMedium★★★★★⏱ O(m * n)

🔍 Binary Search#1011Capacity to Ship Packages Within D DaysMedium★★★★★⏱ O(n * log(sum(weights)))

🗺️ Graphs#1020Number of EnclavesMedium★★★★★⏱ O(m * n)

🪙 Greedy#1029Two City SchedulingMedium★★★★★⏱ O(n log n)

📈 1-D DP#1035Uncrossed LinesMedium★★★★★⏱ O(m * n)

📐 Math & Geometry#1041Robot Bounded In CircleMedium★★★★★⏱ O(n)

⛰️ Heap / Priority Queue#1046Last Stone WeightEasy★★★★★⏱ O(n log n)

🧮 2-D DP#1049Last Stone Weight IIMedium★★★★★⏱ O(n * sum)

📐 Math & Geometry#1071Greatest Common Divisor of StringsEasy★★★★★⏱ O(m + n)

🗺️ Graphs#1091Shortest Path in Binary MatrixMedium★★★★★⏱ O(n^2)

⛰️ Heap / Priority Queue#1094Car PoolingMedium★★★★★⏱ O(n log n)

🗺️ Graphs#1129Shortest Path with Alternating ColorsMedium★★★★★⏱ O(V + E)

📈 1-D DP#1137N-th Tribonacci NumberEasy★★★★★⏱ O(n)

🧮 2-D DP#1140Stone Game IIMedium★★★★★⏱ O(n^3)

🧮 2-D DP#1143Longest Common SubsequenceMedium★★★★★⏱ O(m * n)

🗺️ Graphs#1162As Far from Land as PossibleMedium★★★★★⏱ O(n^2)

🗂️ Arrays & Hashing#1189Maximum Number of BalloonsEasy★★★★★⏱ O(n)

📚 Stack#1209Remove All Adjacent Duplicates In String IIMedium★★★★★⏱ O(n)

🧮 2-D DP#1220Count Vowels PermutationHard★★★★★⏱ O(n)

🔙 Backtracking#1239Maximum Length of a Concatenated String With Unique CharactersMedium★★★★★⏱ O(2^n)

🗺️ Graphs#1254Number of Closed IslandsMedium★★★★★⏱ O(m * n)

📐 Math & Geometry#1260Shift 2D GridEasy★★★★★⏱ O(m * n)

🔍 Binary Search#1268Search Suggestions SystemMedium★★★★★⏱ O(n log n + m * log n * L)

📏 Intervals#1288Remove Covered IntervalsMedium★★★★★⏱ O(n log n)

🗂️ Arrays & Hashing#1299Replace Elements With Greatest Element On Right SideEasy★★★★★⏱ O(n)

🪟 Sliding Window#1343Number of Sub Arrays of Size K and Avg Greater than or Equal to ThresholdMedium★★★★★⏱ O(n)

📈 1-D DP#1359Count all Valid Pickup and Delivery OptionsHard★★★★★⏱ O(n)

🌳 Trees#1376Time Needed to Inform All EmployeesMedium★★★★★⏱ O(n)

⛰️ Heap / Priority Queue#1383Maximum Performance of a TeamHard★★★★★⏱ O(n log n)

🗂️ Arrays & Hashing#1396Design Underground SystemMedium★★★★★⏱ O(1)

⛰️ Heap / Priority Queue#1405Longest Happy StringMedium★★★★★⏱ O((a + b + c) * log 3)

📈 1-D DP#1406Stone Game IIIHard★★★★★⏱ O(n)

🪙 Greedy#1423Maximum Points You Can Obtain From CardsMedium★★★★★⏱ O(n)

🌳 Trees#1443Minimum Time to Collect All Apples in a TreeMedium★★★★★⏱ O(n)

🌳 Trees#1448Count Good Nodes in Binary TreeMedium★★★★★⏱ O(n)

🪟 Sliding Window#1456Maximum Number of Vowels in a Substring of Given LengthMedium★★★★★⏱ O(n)

🗂️ Arrays & Hashing#1461Check if a String Contains all Binary Codes of Size KMedium★★★★★⏱ O(n)

🗺️ Graphs#1462Course Schedule IVMedium★★★★★⏱ O(V^2 + E + Q)

🗺️ Graphs#1466Reorder Routes to Make All Paths Lead to The City ZeroMedium★★★★★⏱ O(n)

🔢 Bit Manipulation#1470Shuffle the ArrayEasy★★★★★⏱ O(n)

🔗 Linked List#1472Design Browser HistoryMedium★★★★★⏱ O(1)

🕸️ Advanced Graphs#1489Find Critical and Pseudo Critical Edges in Minimum Spanning TreeHard★★★★★⏱ O(E^2 * α(V))

👉 Two Pointers#1498Number of Subsequences That Satisfy The Given Sum ConditionMedium★★★★★⏱ O(n log n)

🕸️ Advanced Graphs#1514Path with Maximum ProbabilityMedium★★★★★⏱ O(E log V)

📐 Math & Geometry#1523Count Odd Numbers in an Interval RangeEasy★★★★★⏱ O(1)

🧮 2-D DP#1547Minimum Cost to Cut a StickHard★★★★★⏱ O(c^3)

🗺️ Graphs#1553Minimum Number of Days to Eat N OrangesHard★★★★★⏱ O(log^2(n))

🗺️ Graphs#1557Minimum Number of Vertices to Reach all NodesMedium★★★★★⏱ O(V + E)

📐 Math & Geometry#1572Matrix Diagonal SumEasy★★★★★⏱ O(n)

🕸️ Advanced Graphs#1579Remove Max Number of Edges to Keep Graph Fully TraversableHard★★★★★⏱ O(E * α(V))

🕸️ Advanced Graphs#1584Min Cost to Connect All PointsMedium★★★★★⏱ O(n^2 log n)

🗂️ Arrays & Hashing#1603Design Parking SystemEasy★★★★★⏱ O(1)

📈 1-D DP#1626Best Team with no ConflictsMedium★★★★★⏱ O(n log M)

🕸️ Advanced Graphs#1631Path with Minimum EffortMedium★★★★★⏱ O(m * n * log(m * n))

🧮 2-D DP#1639Number of Ways to Form a Target String Given a DictionaryHard★★★★★⏱ O(m * n)

🪙 Greedy#1647Minimum Deletions to Make Character Frequencies UniqueMedium★★★★★⏱ O(n + k log k)

🪟 Sliding Window#1658Minimum Operations to Reduce X to ZeroMedium★★★★★⏱ O(n)

⛰️ Heap / Priority Queue#1675Minimize Deviation in ArrayHard★★★★★⏱ O(n * log(maxVal) * log n)

🔗 Linked List#1721Swapping Nodes in a Linked ListMedium★★★★★⏱ O(n)

👉 Two Pointers#1768Merge Strings AlternatelyEasy★★★★★⏱ O(n + m)

📈 1-D DP#1799Maximize Score after N OperationsHard★★★★★⏱ O(2^(2n) * n^2)

🗂️ Arrays & Hashing#1822Sign of An ArrayEasy★★★★★⏱ O(n)

⛰️ Heap / Priority Queue#1834Single Threaded CPUMedium★★★★★⏱ O(n log n)

🪟 Sliding Window#1838Frequency of The Most Frequent ElementMedium★★★★★⏱ O(n log n)

⛰️ Heap / Priority Queue#1845Seat Reservation ManagerMedium★★★★★⏱ O(log n)

🔙 Backtracking#1849Splitting a String Into Descending Consecutive ValuesMedium★★★★★⏱ O(n^2)

📏 Intervals#1851Minimum Interval to Include Each QueryHard★★★★★⏱ O((n + q) log n)

📈 1-D DP#1856Maximum Subarray Min ProductMedium★★★★★⏱ O(n)

🗺️ Graphs#1857Largest Color Value in a Directed GraphHard★★★★★⏱ O((V + E) * 26)

🧮 2-D DP#1866Number of Ways to Rearrange Sticks With K Sticks VisibleHard★★★★★⏱ O(n * k)

🪙 Greedy#1871Jump Game VIIMedium★★★★★⏱ O(n)

⛰️ Heap / Priority Queue#1882Process Tasks Using ServersMedium★★★★★⏱ O((n + m) log m)

🪟 Sliding Window#1888Minimum Number of Flips to Make The Binary String AlternatingMedium★★★★★⏱ O(n)

🔍 Binary Search#1898Maximum Number of Removable CharactersMedium★★★★★⏱ O((n + m) * log(removable.size))

🪙 Greedy#1899Merge Triplets to Form Target TripletMedium★★★★★⏱ O(n)

🗺️ Graphs#1905Count Sub IslandsMedium★★★★★⏱ O(m * n)

🧮 2-D DP#1911Maximum Alternating Subsequence SumMedium★★★★★⏱ O(n)

🪙 Greedy#1921Eliminate Maximum Number of MonstersMedium★★★★★⏱ O(n log n)

🗂️ Arrays & Hashing#1929Concatenation of ArrayEasy★★★★★⏱ O(n)

🗂️ Arrays & Hashing#1930Unique Length 3 Palindromic SubsequencesMedium★★★★★⏱ O(26 * n)

🗺️ Graphs#1958Check if Move Is LegalMedium★★★★★⏱ O(8 * 8)

🗂️ Arrays & Hashing#1963Minimum Number of Swaps to Make The String BalancedMedium★★★★★⏱ O(n)

📈 1-D DP#1964Find the Longest Valid Obstacle Course at Each PositionHard★★★★★⏱ O(n log n)

👉 Two Pointers#1968Array With Elements Not Equal to Average of NeighborsMedium★★★★★⏱ O(n log n)

🔙 Backtracking#1980Find Unique Binary StringMedium★★★★★⏱ O(n)

👉 Two Pointers#1984Minimum Difference Between Highest And Lowest of K ScoresEasy★★★★★⏱ O(n log n)

⛰️ Heap / Priority Queue#1985Find the Kth Largest Integer in the ArrayMedium★★★★★⏱ O(n log k * L)

🌳 Trees#1993Operations On TreeMedium★★★★★

🗂️ Arrays & Hashing#2001Number of Pairs of Interchangeable RectanglesMedium★★★★★⏱ O(n log(max(w,h)))

🗂️ Arrays & Hashing#2002Maximum Product of The Length of Two Palindromic SubsequencesMedium★★★★★⏱ O(3^n)

📐 Math & Geometry#2013Detect SquaresMedium★★★★★⏱ O(1)

🗂️ Arrays & Hashing#2017Grid GameMedium★★★★★⏱ O(n)

📐 Math & Geometry#2028Find Missing ObservationsMedium★★★★★⏱ O(m + n)

🗺️ Graphs#2101Detonate the Maximum BombsMedium★★★★★⏱ O(n^3)

🔗 Linked List#2130Maximum Twin Sum Of A Linked ListMedium★★★★★⏱ O(n)

📈 1-D DP#2140Solving Questions With BrainpowerMedium★★★★★⏱ O(n)

🗂️ Arrays & Hashing#2215Find the Difference of Two ArraysEasy★★★★★⏱ O(n + m)

🧮 2-D DP#2218Maximum Value of K Coins from PilesHard★★★★★⏱ O(n * k * max_pile_size)

🔍 Binary Search#2300Successful Pairs of Spells and PotionsMedium★★★★★⏱ O((m + n) * log n)

🗂️ Arrays & Hashing#2306Naming a CompanyHard★★★★★⏱ O(n * m + 26^2 * n)

🗂️ Arrays & Hashing#2348Number of Zero-Filled SubarraysMedium★★★★★⏱ O(n)

🗺️ Graphs#2359Find Closest Node to Given Two NodesMedium★★★★★⏱ O(n)

📈 1-D DP#2369Check if There is a Valid Partition For The ArrayMedium★★★★★⏱ O(n)

📚 Stack#2390Removing Stars From a StringMedium★★★★★⏱ O(n)

🗂️ Arrays & Hashing#2405Optimal Partition of StringMedium★★★★★⏱ O(n)

🕸️ Advanced Graphs#2421Number of Good PathsHard★★★★★⏱ O(n * α(n))

🪙 Greedy#2439Minimize Maximum of ArrayMedium★★★★★⏱ O(n)

📈 1-D DP#2466Count Ways to Build Good StringsMedium★★★★★⏱ O(high)

🗺️ Graphs#2477Minimum Fuel Cost to Report to the CapitalMedium★★★★★⏱ O(n)

🗂️ Arrays & Hashing#2483Minimum Penalty for a ShopMedium★★★★★⏱ O(n)

🗺️ Graphs#2492Minimum Score of a Path Between Two CitiesMedium★★★★★⏱ O(V + E)

⛰️ Heap / Priority Queue#2542Maximum Subsequence ScoreMedium★★★★★⏱ O(n log n)

🔍 Binary Search#2616Minimize the Maximum Difference of PairsMedium★★★★★⏱ O(n log n + n log(max-min))

🌲 Tries#2707Extra Characters in a StringMedium★★★★★⏱ O(n^2 + m)