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Interview Forge helps you practice mock interviews, follow study plans, track career goals, review learning analytics, and prepare across 36 pages.

DSA Interview Questions — Interview Forge

DSA Interview Questions

Original, in-depth guides written by engineers. Each page includes the approach, complexity, follow-ups, and a link to practice with AI feedback.

Two Sum — Interview Question Guide

Arrays & Hashing · Easy

How to solve the Two Sum interview question, with the optimal hash-map approach, complexity analysis, and the follow-ups interviewers love to ask.

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Valid Parentheses — Interview Question Guide

Stacks · Easy

A complete guide to the Valid Parentheses problem: the stack-based matching approach, complexity, and how interviewers extend it with wildcards and nesting limits.

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Merge Intervals — Interview Question Guide

Intervals · Medium

Solve Merge Intervals with the sort-then-sweep approach, understand the edge cases, and prepare for the calendar and meeting-room follow-ups.

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Longest Substring Without Repeating Characters — Guide

Sliding Window · Medium

Master the sliding-window technique on the classic longest-unique-substring problem, with the two-pointer invariant and O(n) solution.

Container With Most Water — Interview Guide

Two Pointers · Medium

The two-pointer proof for Container With Most Water: why moving the shorter line inward is optimal, with complexity and edge cases.

Reverse a Linked List — Interview Guide

Linked Lists · Easy

Both iterative and recursive ways to reverse a singly linked list, with the pointer-manipulation invariant interviewers want to see.

LRU Cache — Interview Guide

Design · Medium

Design an O(1) LRU cache with a hash map plus doubly linked list, the design question that tests data-structure combination skills.

Top K Frequent Elements — Interview Guide

Heaps & Hashing · Medium

Three ways to solve Top K Frequent Elements — heap, bucket sort, and quickselect — and when each is the right answer in an interview.

Number of Islands — Interview Guide

Graphs / DFS-BFS · Medium

Count islands with DFS, BFS, and union-find, and learn the trade-offs interviewers probe on this classic graph problem.

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