Coding & Algorithms Interview Questions
Practice 3,013 real Coding & Algorithms interview questions for 2026. Coding & Algorithms interview questions for top tech firms like Meta, Amazon, Google, Uber, and TikTok — real questions from actual interviews with detailed solutions — to power your interview preparation. This collection is sharply focused on algorithmic patterns (arrays, strings, sliding windows, trees/graphs, dynamic programming, greedy, two-pointers, and hashing), clean, review-ready code, and the explanation skills that distinguish hires. In 2026 expect familiar medium-to-hard problems plus newer twists: AI-enabled or multi-file coding rounds at some companies, more emphasis on explainability and edge-case reasoning, and occasional real-world performance constraints (streaming, concurrency, memory limits). Interviewers evaluate problem framing, algorithm choice, complexity trade-offs, test-case thinking, and communication under time pressure. Best prep mixes pattern-based practice, timed mock interviews, code-review style polishing, and rehearsed explanations of complexity and tradeoffs. Focus your last-mile prep on writing correct, readable code quickly and on explaining why your solution is robust and efficient for production scenarios.
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Minimize travel cost with two cities
You are scheduling candidates to attend an onsite interview. Each candidate i can fly to New York for cost c1[i] or to San Francisco for cost c2[i]. C...
Return a valid task order
You are given n tasks labeled from 0 to n - 1 and a list of prerequisite pairs prerequisites, where each pair [a, b] means task b must be completed be...
Paginate forward and backward through results
You are asked to extend a basic pagination system to support forward and backward navigation, similar to a cursor-based API. You are given: - A zero-i...
Compute task order with prerequisites
Given an integer n representing tasks labeled 0..n-1 and a list of prerequisite pairs (a, b) meaning b must be completed before a, return any valid or...
Solve power jumps and graph tour
This online assessment contained two coding problems: 1. Minimum operations using signed powers of two Given an integer n, you want to make it equal...
Compute meeting rooms and evaluate RPN
You are given two independent coding tasks. Task 1: Minimum number of meeting rooms Given a list of meeting time intervals intervals, where each inter...
Find longest substring with ≥k repeats
Problem You are given: - a string s (consisting of lowercase English letters), and - an integer k. Return the length of the longest contiguous substri...
Design structure for first unique login user
You are given an online stream of user login events. Each event is a user ID (e.g., an integer or string) indicating that this user has just logged in...
Find a Valid Course Order
You are given n courses labeled from 0 to n - 1 and a list of prerequisite pairs. Each pair [course, prerequisite] means prerequisite must be complete...
Implement a balance tracker and interval merger
This screening contained two coding exercises. Part 1: Driver balance tracker You are building an in-memory ledger for a delivery platform. Each updat...
Implement Connect Four game
Question Design and implement the Connect Four game board, player moves, and winner-detection logic. Discuss time/space complexity and possible follow...
Filter hierarchical paths after deletions
Given two arrays: ( 1) paths — slash-delimited hierarchical strings such as "California", "California/San Francisco", "California/San Francisco/7th St...
Check balanced parentheses with multiple bracket types
Given a string containing only parentheses '()', determine whether it is balanced. Follow-up: extend the solution to also support '[]' and '{}' with c...
Implement single-tab browser history navigation
Implement a BrowserSession for a single-tab browser. APIs: - BrowserSession(string homepage): Initialize with homepage; current page starts at homepag...
Compute task order and layered execution
You have N tasks labeled 0..N-1 and prerequisite pairs (a, b) meaning task a must complete before task b can start. Return any valid execution order o...
Set second tree values by subtree sums
Given the roots of two complete binary trees T1 and T2 that have identical structure and the same number of nodes, replace each value in T2 with the s...
Design a data structure to store anagrams
Problem You are building a small in-memory service that stores words and can return all stored words that are anagrams of a query. Design and implemen...
Debug and optimize a card-drawing strategy
You are given a simplified card game engine with unit tests. The game is played using a table of face-up cards; each card has an integer value. On eac...
Convert Samples into Event Intervals
You are given a time-ordered array samples, where samples[i] is the function name observed at integer timestamp i. Convert this trace into a list of e...
Compute subtree sums with tree DFS
You are given an undirected tree with n nodes labeled 1..n and n-1 edges. The tree is rooted at node 1. Each node i has an integer value val[i]. Retur...