README.md

📅 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
  5. [Hard] Expression Add Operators
  6. [Hard] Remove Invalid Parentheses
  7. [Hard] Count of Unique BSTs
  8. [Hard] Word Search

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Month 4: Dynamic Programming (DP) - Part 1

Week 1: Introduction to Dynamic Programming

• Topics: Fundamentals of DP, 1D DP
• Patterns: Memoization, Tabulation
• Practice:
  1. [Easy] Climbing Stairs
  2. [Medium] House Robber
  3. [Medium] House Robber II
  4. [Medium] Decode Ways
  5. [Medium] Maximum Subarray
  6. [Medium] Jump Game
  7. [Medium] Longest Increasing Subsequence
  8. [Hard] Longest Substring with K Distinct Characters

Week 2: Intermediate DP

• Topics: 0/1 Knapsack and Variants
• Patterns: Knapsack, Subset Sum
• Practice:
  1. [Medium] Partition Equal Subset Sum
  2. [Medium] Combination Sum IV
  3. [Medium] Coin Change
  4. [Medium] Target Sum
  5. [Medium] Ones and Zeroes
  6. [Medium] Minimum Subset Sum Difference
  7. [Hard] Word Break

Week 3: Advanced DP - Sequence Alignment

• Topics: Longest Common Subsequence and Variants
• Patterns: Substring and Subsequence Problems
• Practice:
  1. [Medium] Longest Common Subsequence
  2. [Medium] Longest Common Substring
  3. [Medium] Minimum Insertions/Deletions
  4. [Medium] Edit Distance
  5. [Medium] Longest Palindromic Subsequence
  6. [Medium] Sequence Pattern Matching
  7. [Hard] Palindrome Partitioning II
  8. [Hard] Distinct Subsequences

Week 4: Advanced DP - Matrix and Grid Problems

• Topics: 2D DP, Grid Path Problems
• Patterns: Dynamic Programming on Grids
• Practice:
  1. [Easy] Unique Paths
  2. [Medium] Unique Paths II
  3. [Medium] Minimum Path Sum
  4. [Medium] Dungeon Game
  5. [Medium] Cherry Pickup
  6. [Hard] Interleaving String
  7. [Hard] Maximal Rectangle
  8. [Hard] Largest Rectangle in Histogram

Month 5: Greedy Algorithms, Advanced Dynamic Programming, and Heaps

Week 1: Greedy Algorithms - Intermediate Problems

• Topics: Interval Scheduling, Partitioning, Activity Selection
• Patterns: Interval Problems, Greedy Choice Property
• Practice:
  1. [Easy] Best Time to Buy and Sell Stock II
  2. [Medium] Jump Game
  3. [Medium] Jump Game II
  4. [Medium] Gas Station
  5. [Medium] N Meetings in One Room
  6. [Medium] Partition Labels
  7. [Medium] Task Scheduler
  8. [Hard] Minimum Number of Refueling Stops

Week 2: Heaps - Basics and Applications

• Topics: Heap Basics, Priority Queue, Top-K Problems
• Patterns: Min-Heap, Max-Heap
• Practice:
  1. [Easy] Kth Largest Element in a Stream
  2. [Medium] Kth Largest Element in an Array
  3. [Medium] Top K Frequent Elements
  4. [Medium] K Closest Points to Origin
  5. [Medium] Sort Characters By Frequency
  6. [Hard] Find Median from Data Stream
  7. [Hard] Merge K Sorted Lists
  8. [Hard] Sliding Window Maximum

Week 3: Advanced Dynamic Programming - Optimization Problems

• Topics: DP on Trees, Knapsack Variants
• Patterns: 0/1 Knapsack, DP with Trees
• Practice:
  1. [Medium] Partition Equal Subset Sum
  2. [Medium] Ones and Zeroes
  3. [Medium] Coin Change
  4. [Medium] Target Sum
  5. [Medium] Tree Diameter
  6. [Hard] Longest Increasing Path in a Matrix
  7. [Hard] Maximal Square
  8. [Hard] Burst Balloons

Week 4: Advanced Greedy Algorithms & Special Topics

• Topics: Advanced Greedy Techniques, Miscellaneous
• Patterns: Greedy + Dynamic Programming, Hybrid Patterns
• Practice:
  1. [Medium] Minimum Number of Arrows to Burst Balloons
  2. [Medium] Reduce Array Size to The Half
  3. [Medium] Divide Array in Sets of K Consecutive Numbers
  4. [Hard] Minimum Cost to Hire K Workers
  5. [Hard] IPO
  6. [Hard] Maximum Profit in Job Scheduling
  7. [Hard] Candy

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Month 6: Tries, Advanced Data Structures, and Comprehensive Revision

Week 1: Tries and Prefix Trees

• Topics: Trie Basics, String Manipulations with Trie
• Patterns: Trie Structure, Prefix Matching
• Practice:
  1. [Easy] Implement Trie (Prefix Tree)
  2. [Medium] Add and Search Word - Data Structure Design
  3. [Medium] Word Search II
  4. [Medium] Replace Words
  5. [Medium] Design Search Autocomplete System
  6. [Hard] Palindrome Pairs
  7. [Hard] Concatenated Words
  8. [Hard] Maximum XOR of Two Numbers in an Array

Week 2: Segment Trees and Binary Indexed Trees

• Topics: Range Queries, Lazy Propagation
• Patterns: Segment Tree, Fenwick Tree
• Practice:
  1. [Medium] Range Sum Query - Mutable
  2. [Medium] Range Sum Query 2D - Mutable
  3. [Medium] Count of Smaller Numbers After Self
  4. [Medium] Kth Largest Element in an Array
  5. [Hard] Reverse Pairs
  6. [Hard] The Skyline Problem
  7. [Hard] Maximum Sum of Rectangle No Larger Than K

Week 3: Final Revision - Arrays, Strings, Linked Lists

• Topics: Comprehensive Review and Practice
• Practice:
  1. Review top 3-5 questions from Arrays and Strings sections
  2. Review top 3-5 questions from Linked Lists
  3. Practice Mock Interviews with a random mix of problems
  4. Focus on any weak areas or topics that need additional review

Week 4: Final Revision - Trees, Graphs, DP, and Advanced Topics

• Topics: Comprehensive Review and Practice
• Practice:
  1. Review top 3-5 questions from Trees and Graphs
  2. Review top 3-5 questions from Dynamic Programming
  3. Practice Mock Interviews with a random mix of problems
  4. Focus on polishing solutions for harder problems or any weak areas

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