LeetCode Questions List

This page contains a comprehensive list of all LeetCode problems solved in this blog, organized by difficulty level, category, and solution approach.

Summary Statistics

  • Total Posts: 325 (LC problem posts)
  • Easy: 57 problems
  • Medium: 234 problems
  • Hard: 34 problems

Problems by Category

Counts are computed from the Category + Solution Approach columns in the full table by tag matching (a problem can appear in multiple categories).

See the All LeetCode Problems table below for concrete problems in each category.

Solution Approaches Summary

Most Common Approaches

  1. Dynamic Programming (DP) - 39 problems (template)
  2. Monotonic Stack - 9 problems (template)
  3. Binary Search - 20 problems (template)
  4. Hash Map/Set - 45 problems (template)
  5. DFS/BFS - 64 problems (DFS template, BFS template)
  6. Backtracking - 15 problems (template)
  7. Sliding Window - 17 problems (template)
  8. Two Pointers - 38 problems (template)
  9. Trie - 8 problems (template)
  10. Union Find - 10 problems (template)
  11. Sweep Line - 4 problems (template)
  12. Data Structure Design - 33 problems (template)

Tips for Problem Solving

  1. Identify the Pattern: Look for common algorithm patterns (DP, sliding window, etc.)
  2. Start Simple: Begin with brute force, then optimize
  3. Use Data Structures: Choose appropriate DS for the problem
  4. Consider Edge Cases: Handle boundary conditions
  5. Optimize Space/Time: Trade-offs between complexity and efficiency

All LeetCode Problems

Problem Title Difficulty Category Solution Approach Date Added
2 Add Two Numbers Medium Linked List, Recursion Linked List, Recursion, Math, Carry 2025-11-18
3 Longest Substring Without Repeating Characters Medium Sliding Window, Hash Map, String, Two Pointers Sliding Window, Hash Map, String, Two Pointers 2025-10-09
5 Longest Palindromic Substring Medium String, Two Pointers, Dynamic Programming String, Two Pointers, Palindrome, Expand Around Center, Manacher 2026-01-08
18 4Sum Medium Arrays, Two Pointers, Sorting Arrays, Two Pointers, Sorting 2025-11-04
20 Valid Parentheses Easy String, Stack String, Stack, Parentheses, Validation 2025-11-04
22 Generate Parentheses Medium String, Backtracking, Recursion String, Backtracking, Recursion, DFS 2026-01-12
23 Swap Nodes In Pairs Medium Swap Nodes, Recursion, Iterative Swap Nodes, Recursion, Iterative 2025-09-24
23 Merge K Sorted Lists Hard Linked List, Divide And Conquer, Heap Linked List, Divide And Conquer, Heap, Merge 2026-02-15
25 Reverse Nodes In K Group Hard Reverse Nodes, K Group, Recursion Reverse Nodes, K Group, Recursion 2025-09-24
27 Remove Element Easy Array, Two Pointers Array, Two Pointers, In Place 2026-01-26
29 Divide Two Integers Medium Math, Bit Manipulation Bit Manipulation, Math 2026-02-14
32 Longest Valid Parentheses Hard String, Dynamic Programming, Stack String, Dynamic Programming, Stack, Two Pointers, Greedy 2025-11-24
33 Search In Rotated Sorted Array Medium Rotated Array, Search Rotated Array, Search 2025-09-23
34 Find First And Last Position Of Element In Sorted Array Medium Array, Binary Search Array, Binary Search 2026-01-30
35 Search Insert Position Easy Array, Binary Search Array, Binary Search 2026-01-30
36 Valid Sudoku Medium Math, Bit Manipulation Bitmask, Grid, Hash 2026-02-14
38 Count And Say Medium String, Simulation String, Simulation, Run Length Encoding 2026-02-16
42 Trapping Rain Water Hard Two Pointers, Stack, DP Two Pointers, Monotonic Stack, Prefix Suffix, DP 2026-02-17
43 Multiply Strings Medium String, Math, Simulation String, Math, Big Integer, Simulation 2026-02-17
44 Wildcard Matching Hard String, Dynamic Programming, Greedy, Two Pointers String, Dynamic Programming, Greedy, Two Pointers 2026-02-01
45 Jump Game Ii Medium Array, Greedy Array, Greedy, BFS, Optimization 2025-11-18
46 Permutations Medium Backtracking, Recursion Backtracking, Recursion 2025-10-20
47 Permutations Ii Medium Backtracking, Recursion, Duplicates Backtracking, Recursion, Duplicates 2025-10-20
48 Rotate Image Medium Rotate Image, In Place Rotate Image, In Place 2025-09-24
49 Group Anagrams Medium String, Hash Table String, Hash Table, Anagram, Counting 2025-11-18
50 Pow X N Medium Pow Pow 2025-09-25
51 N Queens Hard Array, Backtracking, Recursion Array, Backtracking, Recursion, Constraint Satisfaction 2026-01-12
53 Maximum Subarray Medium Array, Dynamic Programming, Greedy, Divide And Conquer Array, Dynamic Programming, Greedy, Divide And Conquer 2026-01-04
54 Spiral Matrix Medium Spiral Matrix Spiral Matrix 2025-09-25
55 Jump Game Medium Array, Greedy, Dynamic Programming Array, Greedy, Dynamic Programming 2026-01-03
56 Merge Intervals Medium Array, Sorting, Interval Array, Sorting, Intervals, Merge 2025-11-24
59 Spiral Matrix Ii Medium Matrix, Simulation Matrix, Simulation, Spiral 2026-02-18
61 Rotate List Medium Linked List Linked List, Two Pointers 2026-02-28
62 Unique Paths Medium Unique Paths Unique Paths 2025-09-24
63 Unique Paths Ii Medium Array, Dynamic Programming, Matrix Array, Dynamic Programming, Matrix, Grid, Obstacles 2026-01-21
64 Minimum Path Sum Medium Array, Dynamic Programming, Matrix Array, Dynamic Programming, Matrix, Grid 2026-01-10
67 Add Binary Easy String, Math, Bit Manipulation String, Math, Bit Manipulation 2025-12-11
73 Set Matrix Zeroes Medium Array, Matrix Matrix, In Place 2026-04-02
75 Sort Colors Medium Array, Two Pointers, Sorting Array, Two Pointers, Sorting 2025-12-02
77 Combinations Medium Combinations, DFS Combinations, DFS 2025-09-29
77 Combinations Medium Backtracking, Recursion, Combinations Backtracking, Recursion, Combinations 2025-10-20
78 Subsets Medium Backtracking, DFS Backtracking, DFS, Recursion 2026-03-05
79 Word Search Medium Array, Backtracking, Matrix, DFS Array, Backtracking, Matrix, DFS, Recursion 2026-01-12
80 Remove Duplicates From Sorted Array II Medium Array, Two Pointers Array, Two Pointers, In Place 2026-03-01
84 Largest Rectangle In Histogram Hard Stack, Monotonic Stack Stack, Monotonic Stack 2025-10-20
89 Gray Code Medium Gray Code Gray Code 2025-09-25
92 Reverse Linked List II Medium Linked List Linked List, In Place, Head Insertion, Pointer Manipulation 2026-04-16
91 Decode Ways Medium Dynamic Programming Dynamic Programming, String 2026-02-09
93 Restore Ip Addresses Medium Backtracking, String Backtracking, String 2025-11-14
94 Binary Tree Inorder Traversal Easy Tree, DFS Tree, Inorder, Stack 2026-03-06
96 Unique Binary Search Trees Medium Binary Search Trees Binary Search Trees 2025-10-03
100 Same Tree Easy Tree, DFS Tree, DFS, Recursion 2026-01-19
101 Symmetric Tree Easy Tree, DFS Tree, DFS, Recursion 2026-01-19
102 Binary Tree Level Order Traversal Medium Tree, BFS, Binary Tree Tree, BFS, Level Order Traversal, Binary Tree 2026-01-07
103 Binary Tree Zigzag Level Order Traversal Medium Tree, BFS, Binary Tree Tree, BFS, Level Order Traversal, Deque, Binary Tree 2026-01-06
104 Maximum Depth Of Binary Tree Easy Tree, DFS Tree, DFS, BFS, Recursion 2026-01-19
110 Balanced Binary Tree Easy Tree, DFS Tree, Height, Balance 2026-03-06
111 Minimum Depth Of Binary Tree Easy Tree, DFS Tree, DFS, BFS, Recursion 2026-01-19
112 Path Sum Easy Tree, DFS Tree, DFS, Recursion, Backtracking 2026-01-19
112 Path Sum Easy Tree, DFS Tree, Path Sum, DFS 2026-03-06
113 Path Sum II Medium Tree, DFS Tree, Path Sum, Backtracking 2026-03-06
122 Best Time To Buy And Sell Stock Ii Medium Array, Greedy, Dynamic Programming Array, Greedy, Dynamic Programming 2026-01-03
129 Sum Root To Leaf Numbers Medium Tree, DFS Tree, DFS, Recursion, Binary Tree 2025-11-24
131 Palindrome Partitioning Medium Partitioning Partitioning 2025-09-30
133 Clone Graph Medium Graph, DFS, BFS, Clone Graph, DFS, BFS, Clone 2025-10-20
134 Gas Station Medium Greedy, Array Greedy, Prefix Sum 2026-03-22
135 Candy Hard Array, Greedy Array, Greedy 2026-01-04
143 Reorder List Medium Linked List, Two Pointers Linked List, Fast Slow Pointers, Reverse, Merge 2026-04-14
144 Binary Tree Preorder Traversal Easy Tree, DFS Tree, Preorder, Stack 2026-03-06
145 Binary Tree Postorder Traversal Easy Tree, DFS Tree, Postorder, Stack 2026-03-06
146 Lru Cache Medium Design, Data Structures, Hash Map, Linked List Design, Data Structures, Hash Map, Linked List 2025-11-14
146 Lru Cache Medium Design, Data Structures, Hash Map, Linked List Design, Data Structures, Hash Map, Linked List 2025-11-16
146 Lru Cache Medium Design, Data Structures, Hash Map, Linked List Design, Data Structures, Hash Map, Linked List 2025-12-02
150 Evaluate Reverse Polish Notation Medium Reverse Polish Notation, Rpn Reverse Polish Notation, Rpn 2025-09-24
151 Reverse Words In A String Medium String, Two Pointers String, Deque, Two Pointers 2026-03-27
155 Min Stack Medium Stack Stack, Data Structure Design 2026-02-11
162 Find Peak Element Medium Array, Binary Search Array, Binary Search 2026-01-30
1669 Merge In Between Linked Lists Medium Linked List Pointer Rewiring, Dummy Node, Linked List 2026-04-15
187 Repeated Dna Sequences Medium String, Hashing, Sliding Window, Bit Manipulation String, Hashing, Sliding Window, Bit Manipulation 2026-02-27
189 Rotate Array Medium Array Array, Rotation, Two Pointers 2026-01-20
198 House Robber Medium Dynamic Programming, DP Dynamic Programming, DP, Array, Optimization 2025-11-18
200 Number Of Islands Medium DFS, Graph, Matrix DFS, Graph, Matrix, Connected Components 2025-11-20
203 Remove Linked List Elements Easy Linked List, Iteration Linked List, Two Pointers, Dummy Node 2025-11-18
206 Reverse Linked List Easy Linked List, Recursion, Iteration Linked List, Recursion, Iteration 2025-11-16
207 Course Schedule Medium Graph, Topological Sort, Cycle Detection Graph, Topological Sort, Cycle Detection 2025-10-20
208 Implement Trie Medium String, Design, Trie String, Design, Trie, Prefix Tree, Data Structure 2026-01-18
208 Implement Trie (Prefix Tree) Medium Trie, Data Structure Trie, Prefix Tree, Design 2026-03-03
209 Minimum Size Subarray Sum Medium Array, Sliding Window, Binary Search, Prefix Sum Array, Sliding Window, Binary Search, Prefix Sum, Two Pointers 2026-01-26
210 Course Schedule Ii Medium Graph, Topological Sort Graph, Topological Sort 2026-02-08
211 Design Add And Search Words Data Structure Medium String, Design, Trie String, Design, Trie, Wildcard Search, DFS 2026-01-18
211 Design Add And Search Words Data Structure Medium String, Design, Trie String, Design, Trie, Wildcard Search, DFS 2026-01-19
213 House Robber Ii Medium Array, Dynamic Programming Array, Dynamic Programming, DP, Circular Array 2026-01-25
215 Kth Largest Element In An Array Medium Array, Heap, Quickselect, Divide And Conquer Array, Heap, Priority Queue, Quickselect, Divide And Conquer, Sorting 2026-01-05
217 Contains Duplicate Easy Array, Hash Table Array, Set 2026-03-07
218 Skyline Problem Hard Sweep Line, Priority Queue, Data Structures, Union Find Sweep Line, Priority Queue, Data Structures, Union Find 2025-10-05
219 Contains Duplicate II Easy Array, Hash Table, Sliding Window Array, Set, Sliding Window 2026-03-07
221 Maximal Square Medium Array, Matrix, Dynamic Programming Matrix, 2D DP, Square 2026-04-18
223 Rectangle Area Medium Math, Geometry Math, Geometry 2026-04-09
224 Basic Calculator Medium String, Stack, Expression Evaluation String, Stack, Calculator, Expression Evaluation, Parentheses 2025-11-13
226 Invert Binary Tree Easy Tree, DFS Tree, DFS, Recursion 2026-01-19
227 Basic Calculator Ii Medium String, Stack, Expression Evaluation String, Stack, Calculator, Expression Evaluation 2025-11-13
236 Lowest Common Ancestor Of A Binary Tree Medium Tree, DFS Tree, DFS, Recursion, LCA 2026-01-19
238 Product Of Array Except Self Medium Array, Prefix Sum, Two Pointers Array, Prefix Sum, Two Pointers 2026-01-27
239 Sliding Window Maximum Hard Arrays, Deque, Sliding Window, Monotonic Queue Array, Deque, Sliding Window, Monotonic Queue 2025-11-04
240 Search A 2D Matrix Ii Medium Binary Search, Matrix, 2d Array, Divide Conquer, Search, Optimization Binary Search, Matrix, 2d Array, Divide Conquer, Search, Optimization 2025-10-06
242 Valid Anagram Easy String, Hash Table String, Anagram, Counting 2026-03-07
249 Group Shifted Strings Medium String, Hash Table String, Grouping, Shift 2026-03-07
252 Meeting Rooms Easy Array, Sorting, Intervals Array, Sorting, Intervals 2026-02-06
253 Meeting Rooms Ii Medium Array, Sorting, Priority Queue, Two Pointers Array, Sorting, Priority Queue, Two Pointers 2025-12-11
260 Single Number III Medium Array, Bit Manipulation XOR, Bit Manipulation 2026-03-31
261 Graph Valid Tree Medium Graph, Union Find, DFS Graph, Union Find, DFS, Tree 2026-04-01
269 Alien Dictionary Hard Graph, Topological Sort, String Graph, Topological Sort, String, BFS, Kahn 2026-01-14
270 Closest Binary Search Tree Value Easy Binary Search Tree, Tree, Recursion, Binary Search Binary Search Tree, Tree, Recursion, Binary Search 2025-12-30
274 H Index Medium Array, Sorting, Greedy Array, Sorting, H-Index, Greedy 2026-04-17
277 Find The Celebrity Medium Graph, Two Pointers Graph, Two Pointers, Celebrity 2025-11-24
279 Perfect Squares Medium Math, Dynamic Programming, BFS Math, Dynamic Programming, BFS 2025-12-14
281 Zigzag Iterator Medium Design, Iterator Design, Iterator 2025-12-10
285 Inorder Successor In Bst Medium Binary Search Tree, Tree, Inorder Traversal Binary Search Tree, Tree, Inorder Traversal 2025-12-30
286 Walls And Gates Medium Array, Matrix, BFS Array, Matrix, BFS 2025-12-14
300 Longest Increasing Subsequence Medium Dynamic Programming, DP, Binary Search Dynamic Programming, DP, Binary Search 2025-10-17
303 Range Sum Query Immutable Easy Array, Design, Prefix Sum Array, Design, Prefix Sum 2026-01-01
305 Number Of Islands Ii Hard Array, Union Find, Graph Array, Union Find, Disjoint Set, Incremental, Dynamic 2026-01-16
307 Range Sum Query Mutable Medium Array, Segment Tree, Binary Indexed Tree Array, Segment Tree, Binary Indexed Tree, Data Structure 2026-01-16
308 Range Sum Query 2D Mutable Hard Design, Data Structures, Prefix Sum, Matrix Design, Data Structures, Prefix Sum, Matrix 2025-12-31
309 Best Time To Buy And Sell Stock With Cooldown Medium DP, Stock Dynamic Programming, Cooldown 2026-03-20
310 Minimum Height Trees Medium Graph, Tree, Topological Sort, BFS Graph, Tree, Topological Sort, BFS, Peeling Leaves 2026-01-14
314 Binary Tree Vertical Order Traversal Medium Tree, BFS, Vertical Order Tree, BFS, Vertical Order 2025-10-20
315 Count Of Smaller Numbers After Self Hard Array, Binary Search, Divide And Conquer, Binary Indexed Tree, Segment Tree, Merge Sort Array, Fenwick Tree, Binary Indexed Tree, Coordinate Compression, Inversion Count 2026-01-15
315 Count Of Smaller Numbers After Self Hard Array, Binary Search, Divide And Conquer, Binary Indexed Tree, Segment Tree, Merge Sort Array, Fenwick Tree, Binary Indexed Tree, Coordinate Compression, Inversion Count 2026-01-17
316 Remove Duplicate Letters Medium Stack, Monotonic Stack, Greedy Stack, Monotonic Stack, Greedy 2025-10-17
317 Shortest Distance From All Buildings Hard Shortest Distance, Buildings Shortest Distance, Buildings 2025-09-24
322 Coin Change Medium Dynamic Programming, DP, Coin Change Dynamic Programming, DP, Coin Change 2025-10-20
323 Number Of Connected Components In An Undirected Graph Medium Graph, BFS, DFS, Union Find Graph, BFS, Connected Components, Undirected Graph 2026-01-07
324 Wiggle Sort Ii Medium Arrays, Nth Element, Three Way Partition, Index Mapping Array, Wiggle, Nth_element, Partition 2025-11-04
325 Maximum Size Subarray Sum Equals K Medium Array, Hash Table, Prefix Sum Array, Hash Table, Prefix Sum 2026-02-01
327 Count Of Range Sum Hard Array, Divide And Conquer Array, Divide And Conquer, Merge Sort, Segment Tree, Prefix Sum 2026-01-20
329 Longest Increasing Path in a Matrix Medium Matrix, DFS, Dynamic Programming DFS, Memoization, Topological Sort, DAG 2026-04-18
341 Flatten Nested List Iterator Medium Stack, Iterator, Design Stack, Iterator, Nested List 2026-03-24
344 Reverse String Easy Two Pointers, String Two Pointers, String 2025-10-29
346 Moving Average From Data Stream Easy Queue, Sliding Window, Design Queue, Sliding Window, Design 2025-12-14
347 Top K Frequent Elements Medium Array, Hash Table, Heap Array, Hash Table, Heap, Bucket Sort, Quickselect 2025-10-21
348 Design Tic Tac Toe Medium Design, Array Design, Array, Matrix, Optimization 2025-10-21
349 Intersection Of Two Arrays Easy Array, Hash Table Array, Hash Table, Two Pointers, Sorting 2026-01-19
351 Android Unlock Patterns Medium Backtracking, Recursion, Dynamic Programming Backtracking, Recursion, Dynamic Programming 2026-01-02
354 Russian Doll Envelopes Medium Array, Dynamic Programming, Binary Search, Sorting Array, Dynamic Programming, Binary Search, Sorting, Longest Increasing Subsequence 2026-01-25
358 Rearrange String K Distance Apart Hard String, Heap, Greedy String, Heap, Greedy, Scheduling 2026-03-02
360 Sort Transformed Array Medium Array, Two Pointers, Math, Parabola Array, Two Pointers, Math, Parabola 2025-12-31
362 Design Hit Counter Medium Design, Queue, Sliding Window Design, Deque, Sliding Window 2026-03-19
365 Water And Jug Problem Medium Math, Number Theory Gcd, Bezout 2026-03-14
376 Wiggle Subsequence Medium Array, Dynamic Programming, Greedy Array, Dynamic Programming, Greedy 2026-01-04
382 Linked List Random Node Medium Linked List, Reservoir Sampling Linked List, Random, Reservoir Sampling 2026-04-08
383 Ransom Note Easy String, Hash Table String, Counting 2026-03-07
387 First Unique Character In A String Easy String, Hash Table String, Hash Table, Bit Manipulation, Frequency Counting 2026-01-19
389 Find The Difference Easy String, Bit Manipulation, Hash Table String, XOR, Frequency 2026-03-27
392 Is Subsequence Easy String, Two Pointers, Greedy, Dynamic Programming String, Two Pointers, Greedy, Dynamic Programming 2026-01-03
393 Utf 8 Validation Medium Bit Manipulation, String, Array Bit Manipulation, String, Array 2025-12-31
394 Decode String Medium Stack, String Processing Stack, String Processing 2025-10-19
398 Random Pick Index Medium Hash Table, Reservoir Sampling Hash Table, Reservoir Sampling, Design, Randomization 2025-11-24
399 Evaluate Division Medium Disjoint Set, Graph, DFS Disjoint Set, Graph, DFS 2025-12-17
406 Queue Reconstruction By Height Medium Greedy, Sorting, List Greedy, Sorting, List 2025-10-19
408 Valid Word Abbreviation Easy String, Two Pointers String, Two Pointers, Parsing 2025-11-24
409 Longest Palindrome Easy String, Hash Table, Greedy String, Hash Table, Greedy, Bit Manipulation, Palindrome 2026-01-18
409 Longest Palindrome Easy String, Hash Table, Greedy String, Hash Table, Greedy, Bit Manipulation, Palindrome 2026-01-19
416 Partition Equal Subset Sum Medium Dynamic Programming DP, Knapsack 2026-02-11
417 Pacific Atlantic Water Flow Medium DFS, BFS, Graph DFS, BFS, Graph 2025-10-19
418 Sentence Screen Fitting Medium Dynamic Programming, String, Simulation Dynamic Programming, String, Simulation 2025-12-31
419 Battleships In A Board Medium Array, Matrix Array, Matrix, DFS, Battleship 2025-10-21
425 Word Squares Hard Backtracking, Trie, Recursion, String Backtracking, Trie, Recursion, String 2025-12-31
426 Convert Binary Search Tree To Sorted Doubly Linked List Medium Tree, Linked List Tree, Linked List, Bst, Inorder Traversal, Recursion 2025-10-22
429 N Ary Tree Level Order Traversal Medium Tree, BFS, N Ary Tree Tree, BFS, Level Order Traversal, N Ary Tree 2026-01-07
433 Minimum Genetic Mutation Medium Graph, BFS BFS, Shortest Path, String 2026-03-15
435 Non Overlapping Intervals Medium Array, Greedy, Sorting, Intervals, Dynamic Programming Array, Greedy, Sorting, Intervals, Dynamic Programming 2026-01-03
437 Path Sum Iii Medium Tree, DFS, Recursion Tree, DFS, Recursion 2025-10-19
452 Minimum Number Of Arrows To Burst Balloons Medium Array, Greedy, Sorting, Intervals Array, Greedy, Sorting, Intervals 2026-01-03
455 Assign Cookies Easy Array, Greedy, Sorting, Two Pointers Array, Greedy, Sorting, Two Pointers 2026-01-03
460 Lfu Cache Hard Design, Data Structures, Hash Map, Linked List Design, Data Structures, Hash Map, Linked List 2025-11-14
480 Sliding Window Median Hard Arrays, Multiset, Sliding Window, Two Heaps Array, Multiset, Sliding Window, Two Heaps, Median 2025-11-04
485 Max Consecutive Ones Easy Arrays, Sliding Window Array, Sliding Window, Counting 2025-11-04
487 Max Consecutive Ones Ii Medium Array, Dynamic Programming, Sliding Window Array, Dynamic Programming, Sliding Window 2025-12-30
489 Robot Room Cleaner Hard DFS, Backtracking DFS, Backtracking, Robot, Simulation 2025-11-24
494 Target Sum Medium Dynamic Programming, DP, Subset Sum Dynamic Programming, DP, Subset Sum 2025-10-15
496 Next Greater Element I Easy Array, Stack, Monotonic Stack, Hash Table Array, Stack, Monotonic Stack, Hash Table 2025-12-31
498 Diagonal Traverse Medium Array, Matrix, Simulation Array, Matrix, Simulation 2026-01-20
503 Next Greater Element Ii Medium Monotonic Stack, Stack Monotonic Stack, Stack 2025-10-17
509 Fibonacci Number Easy Dynamic Programming, Recursion Dynamic Programming, Recursion, Math, Fibonacci 2025-11-18
523 Continuous Subarray Sum Medium Array, Prefix Sum, Hash Map Array, Prefix Sum, Hash Map, Math 2026-03-04
525 Contiguous Array Medium Arrays, Hash Map, Prefix Sum Array, Hash Map, Prefix Sum, Subarray 2025-11-04
528 Random Pick With Weight Medium Design, Binary Search, Prefix Sum Design, Binary Search, Prefix Sum, Weighted Random 2025-11-24
532 K Diff Pairs In An Array Medium Array, Hash Table Array, Hash Table 2026-02-06
543 Diameter Of Binary Tree Easy Tree, DFS Tree, Diameter, Height 2026-03-06
545 Boundary Of Binary Tree Medium Tree, DFS Tree, DFS, Binary Tree, Boundary Traversal 2025-10-21
547 Number Of Provinces Medium Disjoint Set, DFS, Graph Disjoint Set, DFS, Graph 2025-12-18
560 Subarray Sum Equals K Medium Array, Hash Table, Prefix Sum Array, Hash Table, Prefix Sum 2026-02-01
561 Array Partition Easy Array, Greedy, Sorting Array, Greedy, Sorting 2026-01-03
568 Maximum Vacation Days Hard Dynamic Programming, Graph, Optimization Dynamic Programming, Graph, Optimization 2025-12-31
593 Valid Square Medium Math, Geometry Math, Geometry 2025-12-02
616 Add Bold Tag In String Medium String, Array, Greedy String, Array, Greedy 2025-12-30
621 Task Scheduler Medium Greedy, Counting Array, Greedy, Counting, Scheduling 2026-03-02
622 Design Circular Queue Medium Array, Linked List, Design, Queue Array, Linked List, Design, Queue, Circular Queue, Data Structure 2026-01-24
636 Exclusive Time Of Functions Medium Stack, Parsing Stack, Parsing, Logs, Simulation 2025-10-27
645 Set Mismatch Easy Array, Hash Table, Math Array, Hash Table, Math, Bit Manipulation, Negative Marking 2026-01-19
647 Palindromic Substrings Medium String, Two Pointers String, Two Pointers, Palindrome, Expand Around Center 2025-11-24
648 Replace Words Medium Trie, Hash Set, String Processing Trie, Hash Set, String Processing 2025-10-17
661 Image Smoother Easy Matrix, Array, Simulation Matrix, Array, Simulation 2025-12-30
673 Number Of Longest Increasing Subsequence Medium Array, Dynamic Programming Array, Dynamic Programming, Longest Increasing Subsequence 2026-01-09
681 Next Closest Time Medium String, Simulation, Brute Force String, Simulation, Brute Force 2025-12-30
683 K Empty Slots Medium Sliding Window, Two Pointers, Array Sliding Window, Two Pointers, Array 2025-12-30
684 Redundant Connection Medium Union Find, Dsu, Graph, Cycle Detection, DFS Union Find, Dsu, Graph, Cycle Detection, DFS 2025-12-29
685 Redundant Connection Ii Hard Union Find, Dsu, Graph, Cycle Detection, Directed Graph Union Find, Dsu, Graph, Cycle Detection, Directed Graph 2025-12-30
686 Repeated String Match Medium String Matching, KMP, Rabin Karp, Rolling Hash String Matching, KMP, Rabin Karp, Rolling Hash 2025-12-30
690 Employee Importance Medium DFS, BFS, Hash Table DFS, BFS, Hash Table 2025-12-16
692 Top K Frequent Words Medium Hash Table, Heap, Sorting, String Hash Table, Heap, Sorting, String, Priority Queue 2026-01-08
695 Max Area Of Island Medium DFS, Graph, Matrix DFS, Graph, Matrix 2025-10-20
708 Insert Into A Sorted Circular Linked List Medium Linked List, Circular Linked List, Circular, Insertion, Two Pointers 2025-10-27
713 Subarray Product Less Than K Medium Array, Sliding Window Array, Sliding Window, Two Pointers 2026-03-21
715 Range Module Hard Design, Data Structures, Interval, Map, Tree Map Design, Data Structures, Interval, Map, Tree Map 2025-12-31
717 1 Bit And 2 Bit Characters Easy Array, Parsing Array, Parsing 2025-10-29
721 Accounts Merge Medium Array, Hash Table, String, Union Find, DFS Array, Hash Table, String, Union Find, Disjoint Set, DFS 2026-01-11
729 My Calendar I Medium Array, Binary Search, Design, Ordered Set Array, Binary Search, Design, Ordered Set, Interval, Overlap Detection 2026-01-17
732 My Calendar Iii Hard Array, Binary Search, Design, Segment Tree, Ordered Set Array, Binary Search, Design, Segment Tree, Lazy Propagation, Sweep Line, Difference Array 2026-01-18
739 Daily Temperatures Medium Array, Stack, Monotonic Stack Array, Stack, Monotonic Stack 2026-01-29
743 Network Delay Time Medium Graph, Shortest Path, Dijkstra Graph, Shortest Path, Dijkstra 2026-02-03
752 Open The Lock Medium BFS, Shortest Path, Lock BFS, Shortest Path, Lock 2025-10-20
772 Basic Calculator Iii Hard String, Stack, Recursion, Expression Evaluation String, Stack, Calculator, Recursion, Expression Evaluation, Parentheses 2025-11-13
787 Cheapest Flights Within K Stops Medium Graph, Shortest Path, Dynamic Programming, Bellman Ford Graph, Shortest Path, Dynamic Programming, Bellman Ford 2026-02-04
794 Valid Tic Tac Toe State Medium Tic Tac Toe, Game Validation Tic Tac Toe, Game Validation 2025-09-24
797 All Paths From Source To Target Medium Graph, DFS, Backtracking Graph, DFS, Backtracking 2026-03-12
802 Find Eventual Safe States Medium Graph, DFS, Cycle Detection Graph, DFS, Cycle Detection, Three State Coloring 2026-01-15
841 Keys And Rooms Medium Graph, DFS, BFS Graph, Reachability, Stack, Queue 2026-03-12
843 Guess The Word Hard Array, String, Interactive, Minmax Array, String, Interactive, Minmax 2026-02-02
844 Backspace String Compare Easy String, Two Pointers, Stack String, Two Pointers, Stack, Simulation 2026-01-12
850 Rectangle Area Ii Hard Geometry, Sweep Line, Segment Tree Geometry, Sweep Line, Segment Tree 2025-12-16
860 Lemonade Change Easy Array, Greedy, Simulation Array, Greedy, Simulation 2026-01-03
862 Shortest Subarray With Sum At Least K Hard Array, Sliding Window, Deque, Prefix Sum, Monotonic Deque Array, Sliding Window, Deque, Prefix Sum, Monotonic Deque 2026-01-26
863 All Nodes Distance K In Binary Tree Medium Tree, DFS, BFS Tree, Binary Tree, DFS, BFS, Graph, Recursion 2025-10-25
875 Koko Eating Bananas Medium Array, Binary Search Array, Binary Search 2026-02-06
876 Middle Of The Linked List Easy Linked List, Two Pointers Linked List, Fast Slow 2026-03-10
893 Groups Of Special Equivalent Strings Easy String, Hash String, Hash, Canonical Form 2026-02-15
894 All Possible Full Binary Trees Medium Tree, Dynamic Programming Binary Tree, Recursion, Memoization 2026-04-12
912 Sort An Array Medium Sorting, Merge Sort, Heap Sort, Counting Sort, Data Structures, Divide Conquer Sorting, Merge Sort, Heap Sort, Counting Sort, Data Structures, Divide Conquer 2025-10-06
918 Maximum Sum Circular Subarray Medium Array, Kadane Array, Dynamic Programming, Kadane 2026-03-25
921 Minimum Add To Make Valid Parentheses Medium String, Stack, Greedy String, Stack, Parentheses, Greedy, Counting 2025-11-04
931 Minimum Falling Path Sum Medium DP, Matrix Dynamic Programming, Matrix 2026-03-23
938 Range Sum Of Bst Easy Tree, Bst, DFS Tree, Bst, DFS, Recursion 2025-11-24
969 Pancake Sorting Medium Array, Sorting Array, Sorting, Greedy, Pancake Flip 2025-11-18
973 K Closest Points To Origin Medium Array, Sorting Array, Sorting, Heap, Quickselect 2025-10-21
974 Subarray Sums Divisible By K Medium Array, Hash Table, Prefix Sum Array, Hash Table, Prefix Sum 2026-02-02
981 Time Based Key Value Store Medium Hash Table, Binary Search, Design Hash Table, Binary Search, Design 2026-01-30
983 Minimum Cost For Tickets Medium Dynamic Programming Dynamic Programming, DP, Optimization 2025-11-24
990 Satisfiability Of Equality Equations Medium Connected Components, Graph Coloring, Disjoint Set Connected Components, Graph Coloring, Disjoint Set 2025-10-04
993 Cousins In Binary Tree Easy Tree, BFS, Binary Tree Tree, BFS, Binary Tree, Level Order Traversal 2026-01-07
994 Rotting Oranges Medium Array, Matrix, BFS Array, Matrix, BFS 2025-12-13
1029 Two City Scheduling Medium Array, Greedy, Sorting Array, Greedy, Sorting 2026-01-04
1047 Remove All Adjacent Duplicates In String Easy String, Stack, Two Pointers String, Stack, Two Pointers, In Place 2025-11-24
1087 Brace Expansion Medium Backtracking, String Backtracking, DFS, String Parsing 2026-03-26
1091 Shortest Path In Binary Matrix Medium Graph, BFS Grid, BFS, Shortest Path 2026-03-11
1094 Car Pooling Medium Array, Sorting Array, Sorting, Simulation, Bucket Sort 2025-10-22
1109 Corporate Flight Bookings Medium Array, Prefix Sum, Difference Array Array, Prefix Sum, Difference Array 2026-02-05
1115 Print FooBar Alternately Medium Concurrency, Threading Threading, Semaphore, Condition Variable 2026-03-28
1124 Longest Well Performing Interval Medium Hash Map, Prefix Sum Hash Map, Prefix Sum 2025-10-16
1136 Parallel Courses Hard Graph, Topological Sort, DFS, Dynamic Programming Graph, Topological Sort, DFS, Dynamic Programming, Memoization 2026-01-27
1177 Can Make Palindrome From Substring Medium String, Bit Manipulation, Prefix Sum, Hash Table String, Bit Manipulation, Prefix Sum, Hash Table 2026-01-01
1188 Design Bounded Blocking Queue Medium Concurrency, Design Threading, Semaphore, Queue 2026-03-29
1202 Smallest String With Swaps Medium String, Union Find, Graph String, Dsu, Connected Components 2026-03-09
1206 Design Skiplist Hard Data Structures, Skiplist, Linked List Data Structures, Skiplist, Linked List 2025-12-03
1207 Unique Number Of Occurrences Easy Array, Hash Table Array, Hash Table, Counting 2025-10-20
1209 Remove All Adjacent Duplicates In String Ii Medium String, Stack, Two Pointers String, Stack, Two Pointers, In Place 2025-11-24
1217 Minimum Cost To Move Chips To The Same Position Easy Array, Math, Greedy Array, Math, Greedy 2026-01-04
1233 Remove Sub Folders From The Filesystem Medium Array, String, Trie, Sorting Array, String, Trie, Sorting, Prefix Matching 2026-01-23
1242 Web Crawler Multithreaded Medium Web Crawler, Concurrent Programming Web Crawler, Concurrent Programming 2025-09-24
1247 Minimum Swaps To Make Strings Equal Medium String, Math, Greedy String, Math, Greedy 2026-01-04
1249 Minimum Remove To Make Valid Parentheses Medium String, Stack String, Stack, Parentheses, Validation 2025-10-22
1275 Find Winner On A Tic Tac Toe Game Easy Array, Simulation Array, Simulation, Game 2026-03-03
1319 Number Of Operations To Make Network Connected Medium Graph, Union Find Graph, Dsu, Connected Components 2026-03-10
1328 Break A Palindrome Medium String, Greedy String, Palindrome, Greedy 2026-04-07
1340 Jump Game V Hard Array, Dynamic Programming, DFS, Memoization Array, Dynamic Programming, DFS, Memoization, Recursion 2026-01-10
1344 Angle Between Hands Of A Clock Medium Math, Geometry Math, Geometry, Simulation 2026-03-03
1353 Maximum Number Of Events That Can Be Attended Medium Greedy, Heap, Sorting Greedy, Priority Queue, Scheduling 2026-04-13
1376 Time Needed To Inform All Employees Medium Tree, Graph, DFS, BFS Tree, Graph, DFS, BFS 2026-03-17
1400 Construct K Palindrome Strings Medium String, Greedy, Hash Table String, Greedy, Hash Table 2026-01-04
1424 Diagonal Traverse Ii Medium Array, Matrix, Hash Map, BFS Array, Matrix, Hash Map, BFS 2025-11-17
1438 Longest Continuous Subarray With Absolute Diff Medium Sliding Window, Monotonic Queue Sliding Window, Monotonic Queue 2026-02-12
1443 Minimum Time To Collect All Apples In A Tree Medium Tree, DFS, BFS, Graph Tree, DFS, BFS, Graph 2025-10-20
1448 Count Good Nodes In Binary Tree Medium Tree, DFS, BFS Tree, DFS, BFS 2026-03-18
1488 Avoid Flood In The City Medium Array, Greedy, Binary Search, Set Array, Greedy, Binary Search, Set 2026-02-07
1570 Dot Product Of Two Sparse Vectors Medium Hash Map, Data Structure, Optimization Hash Map, Data Structure, Optimization 2025-10-19
1584 Min Cost To Connect All Points Medium Graph, MST, Union Find Graph, Kruskal, Dsu, Manhattan 2026-03-08
1605 Find Valid Matrix Given Row And Column Sums Medium Array, Matrix, Greedy Array, Matrix, Greedy 2026-01-04
1624 Largest Substring Between Two Equal Characters Easy String, Hash Table String, Hash Table, Substring, Two Pointers 2026-01-19
1650 Lowest Common Ancestor Of A Binary Tree Iii Medium Tree, Binary Tree, LCA Tree, Binary Tree, LCA 2025-10-20
1670 Design Front Middle Back Queue Medium Design, Deque, Data Structure Design, Deque, Data Structure, Two Deques 2026-01-13
1701 Average Waiting Time Medium Array, Simulation Array, Simulation, Greedy 2026-01-19
1710 Maximum Units On A Truck Easy Array, Greedy, Sorting Array, Greedy, Sorting 2026-01-04
1762 Buildings With An Ocean View Medium Array, Stack, Monotonic Stack Array, Stack, Monotonic Stack, Greedy, Two Pointers 2025-11-24
1768 Merge Strings Alternately Easy String, Two Pointers String, Two Pointers 2026-03-27
1801 Number Of Orders In The Backlog Medium Array, Heap, Priority Queue, Simulation Array, Heap, Priority Queue, Simulation, Greedy 2026-01-22
1804 Implement Trie II (Prefix Tree) Medium Trie, Data Structure Trie, Prefix Tree, Design 2026-03-03
1856 Maximum Sum Of Minimum Product Medium Stack, Monotonic Stack, Prefix Sum Stack, Monotonic Stack, Prefix Sum 2025-10-17
1865 Finding Pairs With A Certain Sum Medium Hash Map, Data Structure Hash Map, Data Structure 2025-10-19
1868 Product Of Two Run Length Encoded Arrays Medium Run Length Encoding, Two Pointers, Array Processing Run Length Encoding, Two Pointers, Array Processing 2025-10-20
1870 Minimum Speed To Arrive On Time Medium Binary Search Binary Search, Math 2026-03-30
1944 Number Of Visible People In A Queue Hard Stack, Monotonic Stack Stack, Monotonic Stack 2026-02-09
1962 Remove Stones To Minimize The Total Medium Array, Greedy, Heap Greedy, Max Heap, Priority Queue 2026-04-22
1976 Number Of Ways To Arrive At Destination Medium Dijkstra, Shortest Path, Graph, Dynamic Programming Dijkstra, Shortest Path, Graph, Dynamic Programming 2025-12-28
2043 Simple Bank System Medium Design, Data Structure Design, Data Structure 2025-10-20
2080 Range Frequency Queries Medium Array, Hash Map, Binary Search, Design Array, Hash Map, Binary Search, Design 2026-01-28
2185 Counting Words With A Given Prefix Easy String, Array String, Array, Prefix, Simulation 2026-01-19
2270 Number Of Ways To Split Array Medium Array, Prefix Sum Prefix Sum, Two Pointers 2026-04-06
2342 Max Sum Of A Pair With Equal Sum Of Digits Medium Array, Hash Table Hash Map, Digits 2026-04-11
2365 Task Scheduler II Medium Array, Simulation, Hash Table Simulation, Greedy 2026-04-10
2406 Divide Intervals Into Minimum Number Of Groups Medium Interval, Heap, Sweep Line Intervals, Heap, Sweep Line 2026-03-16
2433 Find The Original Array Of Prefix Xor Medium Array, Bit Manipulation XOR, Prefix 2026-04-05
2461 Maximum Sum Of Distinct Subarrays With Length K Medium Array, Sliding Window Sliding Window, Hash Map 2026-04-09
2466 Count Ways To Build Good Strings Medium Dynamic Programming, DP Dynamic Programming, DP 2025-10-16
2539 Count The Number Of Good Subsequences Medium String, Combinatorics, Hash Map String, Frequency, Combinatorics, Modular Arithmetic 2026-04-19
2571 Minimum Operations To Reduce An Integer To 0 Medium Math, Greedy, Bit Manipulation Greedy, Bit Manipulation, BFS 2026-04-20
2592 Maximize Greatness Of An Array Medium Array, Greedy, Sorting Greedy, Sorting, Two Pointers 2026-04-21
2799 Count Complete Subarrays In An Array Medium Sliding Window, Hash Map Sliding Window, Hash Map 2025-10-17
2952 Minimum Number Of Coins To Be Added Medium Array, Greedy, Sorting Greedy, Sorting, Coverage Range 2026-04-21
3110 Score Of A String Easy String, Array String, Array, Simulation, Ascii 2026-01-18
3112 Minimum Time To Visit Disappearing Nodes Medium Graph, Shortest Path, Dijkstra Graph, Shortest Path, Dijkstra 2026-02-08
3341 Find Minimum Time To Reach Last Room I Medium Graph, Shortest Path, Dijkstra, Grid Graph, Shortest Path, Dijkstra, Grid 2026-02-10
3342 Find Minimum Time To Reach Last Room Ii Medium Graph, Shortest Path, Dijkstra, Grid Graph, Shortest Path, Dijkstra, Grid 2026-02-10
3439 Reschedule Meetings For Maximum Free Time I Medium Array, Intervals, Sliding Window, Prefix Sum Array, Intervals, Sliding Window, Prefix Sum 2026-02-06
3477 Number Of Unplaced Fruits Medium Array, Greedy, Segment Tree Array, Greedy, Segment Tree, Data Structure 2026-01-16

Last updated: April 22, 2026 Total posts (LC problems): 325