The Complete 90-Day DSA Roadmap for Placements 2026

To crack technical coding interviews at top tech employers (Amazon, Microsoft, Oracle, TCS Digital, Cognizant Elevate, Accolite, Juspay), engineering freshers need a structured, topic-by-topic algorithmic roadmap rather than random problem-solving.

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Month 1: Foundations, Linear Data Structures & Recursion

Days 1 - 10: Programming Language Mastery & Time Complexity

• Master your primary coding language: C++ (STL: vector, set, map, priority_queue) OR Java (Collections: ArrayList, HashSet, HashMap, PriorityQueue).
• Big-O Notation: Time Complexity & Space Complexity analysis (O(1), O(log n), O(n), O(n log n), O(n²), O(2ⁿ)).
• Array basics: Prefix Sums, Kadane's Algorithm for Maximum Subarray, Two-Pointer technique.

Days 11 - 20: Strings & Sliding Window

• String manipulations, anagram detection, string reversal without library methods.
• Sliding Window Technique (Fixed-size and Dynamic-size window problems).
• Hashing: Frequency counters, Longest Substring Without Repeating Characters.

Days 21 - 30: Recursion & Backtracking

• Understanding the Call Stack, base conditions, and recursive leap of faith.
• Subset Generation, Permutations of an Array, N-Queens problem, Word Search.

Month 2: Non-Linear Data Structures

Days 31 - 40: Linked Lists, Stacks & Queues

• Singly and Doubly Linked Lists: Reverse a Linked List, Detect Cycle (Floyd's algorithm), Merge Two Sorted Lists.
• Monotonic Stack problems: Next Greater Element, Trapping Rain Water, Largest Rectangle in Histogram.

Days 41 - 55: Binary Trees & Binary Search Trees (BST)

• Tree Traversals: Inorder, Preorder, Postorder (Iterative and Recursive).
• Level-Order Traversal (BFS), Height of Binary Tree, Diameter of Binary Tree.
• Lowest Common Ancestor (LCA), Validate Binary Search Tree, Kth Smallest Element in a BST.

Days 56 - 60: Heaps & Priority Queues

• Min-Heap and Max-Heap implementation.
• Top 'K' Frequent Elements, Merge K Sorted Lists, Find Median from Data Stream.

Month 3: Advanced Algorithms & System Readiness

Days 61 - 75: Graph Algorithms

• Graph Representation: Adjacency List & Matrix.
• Breadth-First Search (BFS) & Depth-First Search (DFS).
• Cycle Detection in Directed and Undirected Graphs.
• Topological Sort (Kahn's Algorithm), Dijkstra's Shortest Path Algorithm.
• Disjoint Set Union (DSU) & Kruskal's Algorithm for Minimum Spanning Tree.

Days 76 - 85: Dynamic Programming (DP)

• Memoization (Top-Down) vs Tabulation (Bottom-Up).
• 1D DP: Climbing Stairs, Frog Jump, House Robber, Coin Change.
• 2D DP: 0/1 Knapsack, Longest Common Subsequence (LCS), Edit Distance, Unique Paths.

Days 86 - 90: Mock Coding Contests & Placement Drills

• Take timed 90-minute contests on LeetCode/HackerRank.
• Practice explaining your code aloud (dry-running test cases) as required in virtual interviews.