keetcoder

Your structured roadmap to mastering data structures & algorithms for LeetCode 🔥 . 150+ classic problems, clean code in C++/Java/Python/Go/JavaScript, detailed explanations, mind maps, and visual guides to help you learn deeply and efficiently.

Array

1. Introduction to Arrays
2. 704.Binary Search
3. 27.Remove Element
4. 977.Squares of a Sorted Array
5. 209.Minimum Size Subarray Sum
6. 59.Spiral Matrix II
7. Array Summary

Linked List

1. Linked List Basics
2. 203.Remove Linked List Elements
3. 707.Design Linked List
4. 206.Reverse Linked List
5. 24.Swap Nodes In Pairs
6. 19.Remove Nth Node From End Of List
7. 160.Intersection Of Two Linked Lists
8. 142.Linked List Cycle II
9. Linked List Summary

Hash Table

1. Introduction to Hash Table
2. 242.Valid Anagram
3. 349.Intersection of Two Arrays
4. 202.Happy Number
5. 1.Two Sum
6. 454.4Sum II
7. 383.Ransom Note
8. 15.3Sum
9. 18.4Sum
10. Hash Table Summary

String

1. 344.Reverse String
2. 541.Reverse String II
3. 151.Reverse Words in a String
4. 28.Implement strStr()
5. 459.Repeated Substring Pattern
6. String Summary

Double Pointers

1. 27.Remove Element
2. 344.Reverse String
3. 151.Reverse Words in a String
4. 206.Reverse Linked List
5. 19.Remove Nth Node From End of List
6. 160.Intersection of Two Linked Lists
7. 142.Linked List Cycle II
8. 15.3Sum
9. 18.4Sum
10. Double Pointers Summary

Stack and Queue

1. Introduction to Stack and Queue
2. 232.Implement Queue using Stacks
3. 225.Implement Stack using Queues
4. 20.Valid Parentheses
5. 1047.Remove All Adjacent Duplicates in String
6. 150.Evaluate Reverse Polish Notation
7. 239.Sliding Window Maximum
8. 347.Top K Frequent Elements
9. Stack and Queue Summary

Binary Tree

1. Introduction to Binary Trees
2. Recursive Traversal of Binary Trees
3. Iterative Traversal of Binary Trees
4. Unified Iterative Method for Binary Trees
5. 102.Binary Tree Level Order Traversal
6. 226.Invert Binary Tree
7. 101.Symmetric Tree
8. 104.Maximum Depth of Binary Tree
9. 111.Minimum Depth of Binary Tree
10. 222.Count Complete Tree Nodes
11. 110.Balanced Binary Tree
12. 257.Binary Tree Paths
13. 404.Sum of Left Leaves
14. 513.Find Bottom Left Tree Value
15. 112.Path Sum
16. 106.Construct Binary Tree from Inorder and Postorder Traversal
17. 654.Maximum Binary Tree
18. 617.Merge Two Binary Trees
19. 700.Search in a Binary Search Tree
20. 98.Validate Binary Search Tree
21. 530.Minimum Absolute Difference in BST
22. 501.Find Mode in Binary Search Tree
23. 236.Lowest Common Ancestor of a Binary Tree
24. 235.Lowest Common Ancestor of a BST
25. 701.Insert into a Binary Search Tree
26. 450.Delete Node in a BST
27. 669.Trim a Binary Search Tree
28. 108.Convert Sorted Array to BST
29. 538.Convert BST to Greater Tree
30. Binary Tree Summary

Backtracking

1. Introduction to Backtracking
2. 77.Combinations
3. 77.Combinations (Optimized)
4. 216.Combination Sum III
5. 17.Letter Combinations of a Phone Number
6. 39.Combination Sum
7. 40.Combination Sum II
8. 131.Palindrome Partitioning
9. 93.Restore IP Addresses
10. 78.Subsets
11. 90.Subsets II
12. 491.Increasing Subsequences
13. 46.Permutations
14. 47.Permutations II
15. Alternative Deduplication in Backtracking
16. 332.Reconstruct Itinerary
17. 51.N-Queens
18. 37.Sudoku Solver
19. Backtracking Summary

Greedy Algorithm

1. Introduction to Greedy Algorithm
2. 455.Assign Cookies
3. 376.Wiggle Subsequence
4. 53.Maximum Subarray
5. 122.Best Time to Buy and Sell Stock II
6. 55.Jump Game
7. 45.Jump Game II
8. 1005.Maximize Sum After K Negations
9. 134.Gas Station
10. 135.Candy
11. 860.Lemonade Change
12. 406.Queue Reconstruction by Height
13. Queue Reconstruction by Height (Vector Explanation)
14. 452.Minimum Number of Arrows to Burst Balloons
15. 435.Non-overlapping Intervals
16. 763.Partition Labels
17. 56.Merge Intervals
18. 738.Monotone Increasing Digits
19. 968.Binary Tree Cameras
20. Greedy Algorithms Summary

Dynamic Programming

1. Introduction to Dynamic Programming
2. 509.Fibonacci Number
3. 70.Climbing Stairs
4. 746.Min Cost Climbing Stairs
5. 62.Unique Paths
6. 63.Unique Paths II
7. 343.Integer Break
8. 96.Unique Binary Search Trees
9. 0-1 Knapsack Theory (Part 1)
10. [0-1 Knapsack Theory (Part 2)](./problems/knapsack-theor