DSA Practice

Personal 4-week data structures & algorithms practice log — solved problems with my own notes on reasoning, plus hand-rolled implementations of core data structures (no built-in dict/sort/etc. where the point is to learn the internals).

Goal: build solid logic fundamentals as a base for lower-level systems work (CUDA, kernel/driver dev, graphics).

Structure

dsa-practice/
├── week1-arrays-strings/     # arrays, strings, two pointers, basic recursion
├── week2-hashtable-linkedlist/  # hash tables, linked lists, stacks, queues
├── week3-trees-graphs/       # binary trees, BST, BFS/DFS
├── week4-dp/                 # dynamic programming intro
└── data-structures/          # hand-rolled implementations from scratch

Each problem gets its own file: NN_problem_name.py. Every file has:

1. The problem statement (short, in my own words)
2. My first approach / where I got stuck
3. The final solution with comments explaining why, not just what

Progress Tracker

Week 1 — Arrays, Strings, Two Pointers, Recursion

• [✓] Two Sum
• [✓] Valid Anagram
• [✓] Contains Duplicate
• [✓] Valid Palindrome
• [✓] Best Time to Buy and Sell Stock
• [✓] Longest Substring Without Repeating Characters
• Hand-roll: Bubble Sort
• Hand-roll: Merge Sort

Week 2 — Hash Tables, Linked Lists, Stack/Queue

• Group Anagrams
• Top K Frequent Elements
• Valid Parentheses
• Reverse Linked List
• Merge Two Sorted Lists
• Linked List Cycle
• Hand-roll: Hash Table (with collision handling)
• Hand-roll: Singly Linked List (insert/delete/reverse)

Week 3 — Trees, Graphs

• Invert Binary Tree
• Maximum Depth of Binary Tree
• Same Tree
• Validate Binary Search Tree
• Binary Tree Level Order Traversal
• Number of Islands (BFS/DFS on a grid)
• Hand-roll: Binary Search Tree (insert/search/in-order traversal)
• Hand-roll: BFS + DFS on a simple graph

Week 4 — Dynamic Programming

• Climbing Stairs
• House Robber
• Coin Change
• Longest Common Subsequence
• Write-up: what I learned this month (link it from this README)

Notes

• Solving on LeetCode, following the NeetCode 150 list roughly in this order.
• Language: Python for now (fastest to focus on logic, not syntax). May redo select problems in C/C++ later since that's closer to what systems/driver roles actually use.