INTERVIEW QUESTIONS
Coding Interview Questions
Curated interview questions with full explanations — problem statement, brute-force solution, optimal solution, time and space complexity, common follow-ups, and how to verbalize your answer under time pressure. Each page is hand-written; nothing here is AI-generated filler.
10 problems and growing. Want a specific one? Email us.
Two Sum
The classic first interview question. Given an array of integers and a target, return indices of the two numbers that add up to target. Brute-force O(n²), optimal O(n) hash map.
Valid Parentheses
Determine if a string of brackets is validly nested. Classic stack problem — the canonical example of when a stack is the right data structure.
Merge Two Sorted Lists
Merge two sorted linked lists into one sorted list. Foundation for merge sort and the top-K family of problems.
Longest Substring Without Repeating Characters
Find the length of the longest substring without repeated characters. The prototypical sliding window problem — appears in almost every FAANG loop.
Container With Most Water
Given an array of heights, find two lines that together with the x-axis form a container holding the most water. Two-pointer optimization from O(n²) to O(n).
3Sum
Find all unique triplets in an array that sum to zero. Classic sort-plus-two-pointer optimization; duplicate handling is the interview trap.
Reverse Linked List
Reverse a singly linked list. The classic linked-list warm-up — interviewers use it to check pointer manipulation fluency before harder list problems.
Maximum Depth of Binary Tree
Find the maximum depth of a binary tree. The canonical tree-recursion warm-up — DFS in three lines, plus a BFS variant for level-by-level.
Number of Islands
Given a 2D grid of 1s and 0s, count the number of distinct islands (connected components of 1s). Classic grid DFS / BFS / Union-Find problem.
Coin Change
Given coin denominations and an amount, find the minimum number of coins to make that amount. The introductory 1D dynamic programming problem.
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