A structured exploration of data structures and algorithms with detailed notes on problem-solving logic, complexity analysis, and design patterns for computational thinking.

This repository contains solutions to LeetCode problems, organized following the NeetCode Roadmap structure for systematic algorithm learning.

• 98. Validate Binary Search Tree - Valid Range DFS
• 100. Same Tree - Recursive DFS
• 102. Binary Tree Level Order Traversal - BFS Template
• 104. Maximum Depth of Binary Tree - DFS/BFS comparison
• 105. Construct Binary Tree from Preorder and Inorder Traversal - Tree Construction
• 110. Balanced Binary Tree - Bottom-up DFS
• 124. Binary Tree Maximum Path Sum - Hard, Arch vs Straight Path
• 144. Binary Tree Preorder Traversal
• 145. Binary Tree Postorder Traversal - Visit Flag Technique
• 173. Binary Search Tree Iterator
• 199. Binary Tree Right Side View - BFS Last Element
• 226. Invert Binary Tree - DFS/BFS comparison
• 230. Kth Smallest Element in a BST - Inorder = Sorted
• 235. Lowest Common Ancestor of a BST - BST Split Point
• 297. Serialize and Deserialize Binary Tree - Hard, Preorder + Null Markers
• 543. Diameter of Binary Tree - Return height, track diameter
• 572. Subtree of Another Tree - Double Recursion
• 1448. Count Good Nodes in Binary Tree - Path Maximum

• 2. Add Two Numbers
• 19. Remove Nth Node From End of List
• 21. Merge Two Sorted Lists
• 23. Merge k Sorted Lists - Hard
• 25. Reverse Nodes in k-Group - Hard
• 138. Copy List with Random Pointer
• 141. Linked List Cycle
• 143. Reorder List
• 146. LRU Cache
• 148. Sort List
• 206. Reverse Linked List
• 287. Find the Duplicate Number - Floyd's Cycle Detection
• 707. Design Linked List
• 876. Middle of the Linked List
• 1472. Design Browser History

• 3. Longest Substring Without Repeating Characters
• 121. Best Time to Buy and Sell Stock
• 424. Longest Repeating Character Replacement
• 1343. Number of Sub-arrays of Size K and Average Greater than or Equal to Threshold

• 4. Median of Two Sorted Arrays - Hard
• 33. Search in Rotated Sorted Array
• 74. Search a 2D Matrix
• 153. Find Minimum in Rotated Sorted Array
• 278. First Bad Version
• 704. Binary Search
• 981. Time Based Key-Value Store

• 20. Valid Parentheses
• 227. Basic Calculator II
• 496. Next Greater Element I
• 622. Design Circular Queue
• 641. Design Circular Deque
• 739. Daily Temperatures
• 853. Car Fleet
• 1700. Number of Students Unable to Eat Lunch

• 11. Container With Most Water
• 15. 3Sum
• 26. Remove Duplicates from Sorted Array
• 88. Merge Sorted Array
• 167. Two Sum II - Input Array Is Sorted
• 349. Intersection of Two Arrays

• 1. Two Sum
• 28. Find the Index of the First Occurrence in a String
• 128. Longest Consecutive Sequence
• 217. Contains Duplicate
• 242. Valid Anagram
• 506. Relative Ranks
• 724. Find Pivot Index
• 912. Sort an Array
• 1122. Relative Sort Array

• 215. Kth Largest Element in an Array

• 48. Rotate Image
• 498. Diagonal Traverse

Each problem is organized in its own folder with:

• solution.py - Solution code with multiple approaches when applicable
• README.md - Problem description, algorithm explanation, complexity analysis, and key concepts

├── 01-Arrays-and-Hashing/
│   ├── 1. Two Sum/
│   │   ├── solution.py
│   │   └── README.md
│   └── ...
├── 02-Two-Pointers/
│   └── ...
└── ...

1. Follow the Roadmap: Start from 01-Arrays-and-Hashing and progress sequentially
2. Read the Notes: Each problem folder contains solution code and detailed explanations
3. Practice: Try solving problems before looking at solutions
4. Review: Revisit completed topics to reinforce learning

• LeetCode - All problems in this repository are sourced from LeetCode

• NeetCode Roadmap - Structured approach to mastering coding interviews
• NeetCode 150 - Curated list of 150 essential problems

• Language: Python 3.x
• Package Manager: uv

This project is licensed under the terms specified in the LICENSE file.