Patterns Track

Concept difficulty progression from fundamentals to advanced topics.

Solved: 0 / 185

1. Arrays & Hashing

8 problems
Two Pointers ArrayHash Map/Set
#217 easy Contains Duplicate #242 easy Valid Anagram #1 medium Two Sum #36 medium Valid Sudoku #49 medium Group Anagrams #128 medium Longest Consecutive Sequence #238 medium Product of Array Except Self #347 medium Top K Frequent Elements

2. Two Pointers

6 problems
Two Pointers ArrayHash Map/Set
#125 easy Valid Palindrome #11 medium Container With Most Water #15 medium 3Sum #167 medium Two Sum II - Input Array Is Sorted #392 medium Is Subsequence #42 hard Trapping Rain Water

3. Sliding Window

7 problems
Sliding WindowTwo PointersBacktracking Hash Map/SetTreeArray
#121 easy Best Time to Buy and Sell Stock #3 medium Longest Substring Without Repeating Characters #209 medium Minimum Size Subarray Sum #424 medium Longest Repeating Character Replacement #485 medium Max Consecutive Ones #567 medium Permutation in String #76 hard Minimum Window Substring

4. Stack

4 problems
StackTrieArray
#20 easy Valid Parentheses #150 medium Evaluate Reverse Polish Notation #155 medium Min Stack #739 medium Daily Temperatures

5. Binary Search

7 problems
Two PointersBinary SearchRecursionBacktracking ArrayHash Map/SetStack
#69 easy Sqrt(x) #704 easy Binary Search #33 medium Search in Rotated Sorted Array #74 medium Search a 2D Matrix #153 medium Find Minimum in Rotated Sorted Array #875 medium Koko Eating Bananas #4 hard Median of Two Sorted Arrays

6. Linked List

9 problems
Two PointersBinary SearchRecursion ArrayLinked ListHash Map/SetStack
#21 easy Merge Two Sorted Lists #141 easy Linked List Cycle #206 easy Reverse Linked List #2 medium Add Two Numbers #19 medium Remove Nth Node From End of List #138 medium Copy List with Random Pointer #143 medium Reorder List #23 hard Merge k Sorted Lists #25 hard Reverse Nodes in k-Group

7. Trees

12 problems
Two PointersBinary SearchDFSBFSRecursion TreeQueue/DequeArrayHash Map/SetStack
#100 easy Same Tree #104 easy Maximum Depth of Binary Tree #226 easy Invert Binary Tree #235 easy Lowest Common Ancestor of a Binary Search Tree #572 easy Subtree of Another Tree #98 medium Validate Binary Search Tree #105 medium Construct Binary Tree from Preorder and Inorder Traversal #110 medium Balanced Binary Tree #199 medium Binary Tree Right Side View #230 medium Kth Smallest Element in a BST #543 medium Diameter of Binary Tree #124 hard Binary Tree Maximum Path Sum

8. Intervals

5 problems
ArrayHash Map/Set
#252 easy Meeting Rooms #56 medium Merge Intervals #57 medium Insert Interval #251 medium Employee Free Time #253 medium Meeting Rooms II

9. Bit Manipulation

6 problems
RecursionTwo Pointers StackHash Map/SetArray
#190 easy Reverse Bits #191 easy Number of 1 Bits #268 easy Missing Number #371 medium Sum of Two Integers #461 medium Hamming Distance #201 hard Bitwise AND of Numbers Range

10. Backtracking

8 problems
BacktrackingRecursion ArrayHash Map/SetStack
#39 medium Combination Sum #40 medium Combination Sum II #46 medium Permutations #77 medium Combinations #78 medium Subsets #90 medium Subsets II #698 medium Partition to K Equal Sum Subsets #51 hard N-Queens

11. Dynamic Programming

32 problems
Dynamic ProgrammingBinary SearchPrefix SumRecursionDFSGreedy TreeArrayHash Map/SetTrie
#70 easy Climbing Stairs #338 easy Counting Bits #5 medium Longest Palindromic Substring #53 medium Maximum Subarray #62 medium Unique Paths #63 medium Unique Paths II #64 medium Minimum Path Sum #72 medium Edit Distance #91 medium Decode Ways #97 medium Interleaving String #122 medium Best Time to Buy and Sell Stock II #139 medium Word Break #152 medium Maximum Product Subarray #198 medium House Robber #213 medium House Robber II #221 medium Maximal Square #279 medium Perfect Squares #300 medium Longest Increasing Subsequence #309 medium Best Time to Buy and Sell Stock with Cooldown #322 medium Coin Change #376 medium Wiggle Subsequence #377 medium Combination Sum IV #518 medium Coin Change II #583 medium Delete Operation for Two Strings #647 medium Palindromic Substrings #746 medium Min Cost Climbing Stairs #946 medium Distinct Substrings (LeetCode 1698) #983 medium Minimum Cost For Tickets #1143 medium Longest Common Subsequence #10 hard Regular Expression Matching #123 hard Best Time to Buy and Sell Stock III #132 hard Palindrome Partitioning II

12. Greedy

4 problems
Greedy ArrayHash Map/Set
#605 easy Can Place Flowers #55 medium Jump Game #135 medium Candy #452 medium Minimum Number of Arrows to Burst Balloons

13. Stack / Backtracking

1 problems
BacktrackingRecursion Stack
#22 medium Generate Parentheses

14. Arrays & Hashing (with constraints)

1 problems
ArrayHash Map/Set
#41 hard First Missing Positive

15. Greedy / BFS

1 problems
BFSGreedy Array
#45 medium Jump Game II

16. Math & Geometry

6 problems
ArrayHash Map/Set
#66 easy Plus One #48 medium Rotate Image #50 medium Pow(x, n) #73 medium Set Matrix Zeroes #223 medium Rectangle Area #149 hard Max Points on a Line

17. Math & Geometry - Simulation

1 problems
Recursion ArrayHash Map/Set
#54 medium Spiral Matrix

18. Backtracking / DFS

1 problems
DFSBacktracking
#79 medium Word Search

19. Stack - Monotonic Stack

1 problems
Monotonic Stack ArrayStack
#84 hard Largest Rectangle in Histogram

20. Trees / BFS

2 problems
BFS Queue/DequeTree
#102 medium Binary Tree Level Order Traversal #103 medium Binary Tree Zigzag Level Order Traversal

21. Graphs - BFS

1 problems
BFS Hash Map/SetQueue/DequeGraph
#127 hard Word Ladder

22. Backtracking / DP

1 problems
Dynamic ProgrammingBacktracking Tree
#131 medium Palindrome Partitioning

23. Graphs / DFS

4 problems
DFSRecursionBFSUnion Find Hash Map/SetGraphArray
#133 medium Clone Graph #200 medium Number of Islands #417 medium Pacific Atlantic Water Flow #695 medium Max Area of Island

24. Greedy / String

1 problems
Greedy Hash Map/Set
#179 medium Largest Number

25. Graphs / Topological Sort

1 problems
DFSTopological Sort ArrayGraph
#207 medium Course Schedule

26. Tries - Prefix Tree

1 problems
ArrayHash Map/SetTreeTrie
#208 medium Implement Trie (Prefix Tree)

27. Trie / Data Structure Design

1 problems
Hash Map/SetTrie
#211 medium Design Add and Search Words Data Structure

28. Backtracking / Trie

1 problems
DFSBacktrackingRecursion Hash Map/SetTrieArray
#212 hard Word Search II

29. Heap / Priority Queue

5 problems
BFSHeapBacktracking ArrayQueue/DequeHeapHash Map/Set
#1046 easy Last Stone Weight #215 medium Kth Largest Element in an Array #621 medium Task Scheduler #703 medium Kth Largest Element in a Stream #973 medium K Closest Points to Origin

30. Graphs / Trees

1 problems
DFS ArrayHash Map/SetTreeGraph
#261 hard Graph Valid Tree

31. NeetCode 150

36 problems
#271 medium Encode and Decode Strings #295 medium Find Median from Data Stream #355 medium Design Twitter #981 medium Time Based Key-Value Store #100020 medium Sliding Window Maximum #100026 medium Car Fleet #100043 medium LRU Cache #100055 medium Count Good Nodes in Binary Tree #100078 medium Letter Combinations of a Phone Number #100084 medium Surrounded Regions #100086 medium Walls and Gates #100088 medium Course Schedule II #100089 medium Redundant Connection #100090 medium Number of Connected Components in an Undirected Graph #100093 medium Reconstruct Itinerary #100094 medium Min Cost to Connect All Points #100095 medium Network Delay Time #100096 medium Swim in Rising Water #100097 medium Alien Dictionary #100098 medium Cheapest Flights Within K Stops #100110 medium Partition Equal Subset Sum #100115 medium Target Sum #100117 medium Longest Increasing Path in a Matrix #100118 medium Distinct Subsequences #100120 medium Burst Balloons #100125 medium Gas Station #100126 medium Hand of Straights #100127 medium Merge Triplets to Form Target Triplet #100128 medium Partition Labels #100129 medium Valid Parenthesis String #100135 medium Minimum Interval to Include Each Query #100139 medium Happy Number #100142 medium Multiply Strings #100143 medium Detect Squares #100144 medium Single Number #100150 medium Reverse Integer

32. Blind 75

4 problems
#271 medium Encode and Decode Strings #295 medium Find Median from Data Stream #200032 medium Alien Dictionary #200034 medium Number of Connected Components in an Undirected Graph

33. Linked List / Floyd's Algorithm

1 problems
ArrayLinked List
#287 medium Find the Duplicate Number

34. Trees / DFS

1 problems
DFSRecursion Tree
#297 hard Serialize and Deserialize Binary Tree

35. Greedy / Sorting

1 problems
BFSGreedy ArrayQueue/Deque
#406 medium Queue Reconstruction by Height

36. Intervals / Greedy

1 problems
Greedy Array
#435 medium Non-overlapping Intervals

37. Backtracking / Memoization

1 problems
DFSBacktrackingRecursion Hash Map/Set
#464 medium Can I Win

38. Graphs / BFS

1 problems
BFS Queue/DequeGraph
#994 medium Rotting Oranges