data-structures-algorithms

Six-Month DSA Study Plan

Overview

This structured six-month plan gradually introduces core DSA concepts and patterns, with 8-10 carefully selected practice questions each week. By the end of this plan, you’ll have covered foundational topics and advanced concepts needed for top-tier technical interviews.

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Special Resources

1. 20 Patterns to Crack MAANG
2. 14 Tricks to Identify Patterns

Month 1: Arrays and Strings

Week 1: Arrays Basics & Simple Patterns

• Topics: Two-pointer, Sliding Window, HashMap basics
• Patterns: Prefix Sum, Running Sum
• Practice:
  1. [Easy] Two Sum
  2. [Easy] Contains Duplicate
  3. [Easy] Maximum Subarray (Kadane’s Algorithm)
  4. [Medium] Best Time to Buy and Sell Stock
  5. [Medium] Product of Array Except Self
  6. [Medium] Subarray Sum Equals K
  7. [Medium] Longest Subarray with Sum K
  8. [Medium] Minimum Size Subarray Sum

Week 2: Advanced Array Manipulations

• Topics: Sorting, Interval Overlap, Cyclic Sort
• Patterns: Sorting + Two-pointer, Merge Intervals
• Practice:
  1. [Easy] Sort Colors (Dutch National Flag Problem)
  2. [Medium] Merge Intervals
  3. [Medium] Set Matrix Zeroes
  4. [Medium] Next Permutation
  5. [Medium] Rotate Image
  6. [Medium] Find the Duplicate Number
  7. [Medium] Kth Largest Element in an Array
  8. [Medium] First Missing Positive

Week 3: Strings - Basics and Manipulations

• Topics: HashMaps for Strings, Substrings
• Patterns: Sliding Window, Hashing
• Practice:
  1. [Easy] Longest Common Prefix
  2. [Easy] Valid Anagram
  3. [Medium] Longest Substring Without Repeating Characters
  4. [Medium] Minimum Window Substring
  5. [Medium] Find All Anagrams in a String
  6. [Medium] Group Anagrams
  7. [Medium] Longest Palindromic Substring
  8. [Medium] Decode Ways

Week 4: Advanced String Manipulations

• Topics: Substrings and Subsequence
• Patterns: Two-pointer, Dynamic Programming (DP) for Strings
• Practice:
  1. [Easy] Implement strStr()
  2. [Medium] Longest Common Subsequence
  3. [Medium] Edit Distance
  4. [Medium] Palindromic Substrings
  5. [Medium] Partition Labels
  6. [Hard] Minimum Window Substring
  7. [Hard] Substring with Concatenation of All Words
  8. [Hard] Wildcard Matching

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Month 2: Linked Lists and Binary Trees

Week 1: Linked Lists Basics

• Topics: Singly and Doubly Linked Lists, Basic Operations
• Patterns: Two-pointer, Fast & Slow Pointers
• Practice:
  1. [Easy] Reverse Linked List
  2. [Easy] Middle of the Linked List
  3. [Medium] Linked List Cycle
  4. [Medium] Intersection of Two Linked Lists
  5. [Medium] Add Two Numbers
  6. [Medium] Remove N-th Node from End
  7. [Medium] Flatten a Multilevel Doubly Linked List
  8. [Hard] Merge K Sorted Lists

Week 2: Advanced Linked Lists

• Topics: Complex List Manipulations, Reversal in Groups
• Patterns: Fast & Slow Pointers, Recursive Linked List
• Practice:
  1. [Medium] Reverse Nodes in k-Group
  2. [Medium] Rotate List
  3. [Medium] Copy List with Random Pointer
  4. [Medium] Partition List
  5. [Medium] LRU Cache
  6. [Hard] LRU Cache
  7. [Hard] Reverse Nodes in k-Group
  8. [Hard] Insert into a Cyclic Sorted List

Week 3: Binary Trees Basics

• Topics: Binary Tree Traversals (Inorder, Preorder, Postorder)
• Patterns: DFS and BFS Traversals
• Practice:
  1. [Easy] Binary Tree Inorder Traversal
  2. [Easy] Binary Tree Preorder Traversal
  3. [Easy] Binary Tree Postorder Traversal
  4. [Medium] Binary Tree Level Order Traversal
  5. [Medium] Binary Tree Zigzag Level Order Traversal
  6. [Medium] Binary Tree Right Side View
  7. [Medium] Binary Tree Left Side View
  8. [Medium] Binary Tree Maximum Path Sum

Week 4: Advanced Trees

• Topics: Tree Properties, Recursive & Iterative Solutions
• Patterns: Depth-First Search, Breadth-First Search
• Practice:
  1. [Easy] Symmetric Tree
  2. [Medium] Lowest Common Ancestor of a Binary Tree
  3. [Medium] Binary Tree Level Order Traversal II
  4. [Medium] Serialize and Deserialize Binary Tree
  5. [Medium] Populating Next Right Pointers in Each Node
  6. [Hard] Recover Binary Search Tree
  7. [Hard] Flatten Binary Tree to Linked List
  8. [Hard] Binary Tree Cameras

Month 3: Graphs and Recursion

Week 1: Graphs Basics

• Topics: Graph Representations, BFS, DFS
• Patterns: Breadth-First Search, Depth-First Search
• Practice:
  1. [Easy] Flood Fill
  2. [Medium] Number of Islands
  3. [Medium] Surrounded Regions
  4. [Medium] Rotting Oranges
  5. [Medium] Word Ladder
  6. [Medium] Clone Graph
  7. [Medium] Course Schedule
  8. [Medium] Detect Cycle in Undirected Graph
  9. [Hard] Minimum Number of Swaps for Sorting

Week 2: Advanced Graph Algorithms

• Topics: Topological Sort, Connected Components
• Patterns: Topological Sort, Union-Find
• Practice:
  1. [Medium] Alien Dictionary
  2. [Medium] Course Schedule II
  3. [Medium] Reconstruct Itinerary
  4. [Medium] Connected Components in Graph
  5. [Medium] Accounts Merge
  6. [Hard] Find Critical and Pseudo-Critical Edges
  7. [Hard] Redundant Connection
  8. [Hard] Graph Valid Tree

Week 3: Recursion and Backtracking

• Topics: Basics of Recursion, Permutations, Combinations
• Patterns: Backtracking, DFS
• Practice:
  1. [Easy] Subsets
  2. [Medium] Combination Sum
  3. [Medium] Permutations
  4. [Medium] Palindrome Partitioning
  5. [Hard] N-Queens
  6. [Hard] Sudoku Solver
  7. [Hard] Word Search II
  8. [Hard] K-th Permutation Sequence

Week 4: Advanced Backtracking Problems

• Topics: Constraint Satisfaction, Optimizations
• Patterns: Recursion + Memoization
• Practice:
  1. [Medium] Generate Parentheses
  2. [Medium] Letter Combinations of a Phone Number
  3. [Medium] Partition to K Equal Sum Subsets
  4. [Hard] [Restore IP Addresses](https://leetcode.com/problems