KhokonChandra.

🚀 4-Week DSA Roadmap for PHP Developers

⏳ Duration: 4 Weeks (~2-3 problems per day)
🛠️ Goal: Solve 50+ key DSA problems before the coding test
💻 Practice Platform: LeetCode, GeeksForGeeks, InterviewBit

📅 Week 1: Mastering Arrays & Hashing

Focus: Arrays, Hashing, Two Pointers, Sliding Window
🔥 Key Concepts: Sorting, Frequency counting, Prefix sum, Kadane’s algorithm

📝 Day 1-2: Basic Array Operations & Two Pointers

  1. Two Sum 🟢
  2. Best Time to Buy and Sell Stock 🟢
  3. Contains Duplicate 🟢
  4. Remove Duplicates from Sorted Array 🟢

📝 Day 3-4: Sliding Window & Prefix Sum

  1. Maximum Subarray (Kadane’s Algorithm) 🔵
  2. Longest Substring Without Repeating Characters 🔵
  3. Sliding Window Maximum 🔴

📝 Day 5-7: HashMaps & Sorting

  1. Group Anagrams 🔵
  2. Valid Anagram 🟢
  3. Longest Consecutive Sequence 🔵

📅 Week 2: Linked List, Stack & Queues

Focus: Linked Lists, Stack & Queue operations
🔥 Key Concepts: Fast & slow pointers, LRU cache, Parentheses validation

📝 Day 8-9: Linked List Basics

  1. Reverse Linked List 🟢
  2. Merge Two Sorted Lists 🟢

📝 Day 10-11: Fast & Slow Pointers

  1. Linked List Cycle 🔵
  2. Find the Middle of Linked List 🟢
  3. Remove Nth Node from End of List 🔵

📝 Day 12-13: Stacks & Queues

  1. Valid Parentheses 🟢
  2. Next Greater Element 🔵
  3. Implement Queue using Stack 🔵

📝 Day 14: Advanced Stack Problem

  1. LRU Cache 🔴

📅 Week 3: Trees & Graphs

Focus: Binary Trees, Graphs (DFS & BFS), Shortest Paths
🔥 Key Concepts: Recursion, BFS/DFS, Binary Search Tree (BST), Dijkstra’s Algorithm

📝 Day 15-16: Tree Traversals

  1. Binary Tree Inorder Traversal 🟢
  2. Invert Binary Tree 🟢

📝 Day 17-18: Binary Search Tree (BST)

  1. Lowest Common Ancestor of a BST 🔵
  2. Diameter of a Binary Tree 🔵

📝 Day 19-20: Graphs (DFS & BFS)

  1. Number of Islands 🔵
  2. Detect Cycle in Directed Graph 🔵

📝 Day 21: Advanced Graphs

  1. Dijkstra’s Algorithm (Shortest Path) 🔴
  2. Topological Sorting 🔴

📅 Week 4: Dynamic Programming & Recursion

Focus: Recursion, Backtracking, DP problems
🔥 Key Concepts: Fibonacci DP, LCS, Knapsack

📝 Day 22-23: Recursion & Backtracking

  1. Subsets 🔵
  2. Word Search 🔵

📝 Day 24-25: Dynamic Programming Basics

  1. Climbing Stairs (Fibonacci-based DP) 🟢
  2. Longest Common Subsequence 🔵

📝 Day 26-27: Advanced DP

  1. Coin Change 🔵
  2. 0/1 Knapsack Problem 🔵

📝 Day 28: Final Challenge (Hard DP)

  1. N-Queens 🔴

🚀 Final Week: Mock Tests & Practice

  • Solve random problems from LeetCode Medium/Hard
  • Try PHP-based implementations for some problems
  • Take a full-length timed test (e.g., 90 minutes, 2-3 problems)

💡 Pro Tips for PHP Developers

✅ Use PHP’s built-in functions for arrays (array_map(), array_filter())
✅ Use associative arrays (hashmaps) efficiently
✅ Write clean OOP-based PHP solutions
✅ Test solutions with edge cases (empty input, large numbers, negative values)