Top 50 DSA Problems for Coding Interviews

Why This List Matters

Interviewers at companies like Google, Meta, Amazon, and Microsoft tend to draw from a relatively small pool of classic problems. Mastering these gives you a strong foundation.

Arrays and Strings

Two Sum

The classic hash map problem. Given an array and target, return indices of two numbers that add up to the target.

Sliding Window Maximum

Use a deque to maintain candidates and get the maximum in each window in O(n).

Linked Lists and Trees

Reverse a Linked List

Iterative and recursive approaches. Know both.

Binary Tree Level Order Traversal

BFS with a queue. Often extended to level-by-level formatting.

Dynamic Programming

Climbing Stairs

Classic 1D DP. Then generalize to "min cost" and "number of ways."

Longest Increasing Subsequence

O(n²) and O(n log n) solutions.

Summary

Focus on patterns: two pointers, sliding window, DFS/BFS, DP, and binary search. Use Preplume(/) to track your progress and revise systematically.