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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Determine Balloon Popping Time
You are given a rectangular 2D grid representing a field of balloons. Each cell contains exactly one of the following values: - 0: empty cell - 1: inf...
Maximize coins with tokens moving by +3
You are given a 1D board represented by a string s of length n. Each character is one of: - '.' — an empty cell - 'C' — a cell containing exactly one ...
Compute nearest bathroom distance for each desk
You are given an m x n grid of characters containing only: - 'B' = bathroom - 'D' = desk - '_' = empty cell From any cell you may move one step up/dow...
Print the File System State
You are given a toy in-memory file system represented as an ordered sequence of disk blocks. Each block contains zero or more file records, such as fi...
Find Shortest Wiki Click Path
Implement a function that computes the minimum number of clicks needed to navigate from one wiki page to another. You are given two page URIs, start_u...
Implement spreadsheet cells with formulas
Design an in-memory spreadsheet that supports these operations on cells such as A1, B2, and ranges such as A1:B2: - Set(cell, value): assign an intege...
Merge Overlapping Collinear Segments
You are given a list of 2D geometric segments: vector<vector<pair<double, double>>> segments Each inner list represents one segment and contains at le...
Implement array merge, round-robin scheduler, and trading simulator
You are given three independent coding prompts. For each prompt, clearly define your function/class interfaces, handle edge cases, and analyze time/sp...
Compute rainwater accumulation on a height grid
Mountain Rainfall Accumulation You are given an m x n 2D integer grid elevation, where elevation[r][c] is the terrain height at cell (r, c). Assume 1 ...
Implement banking, knapsack, and pagination tasks
Problem A — Banking system command processor Implement an in-memory banking system that processes a sequence of commands in timestamp order. Entities ...
Find kth element and sliding-window kth in stream
You are given two related tasks. Task 1: Kth element in an array Given an integer array nums of length n and an integer k (1-indexed), return the k-th...
Build a hit/miss word guessing game
Two players play a word guessing game. - Player A chooses a secret word. - Player B repeatedly guesses single letters. - After each guess, the game re...
Implement Last-Click Attribution APIs
Design and implement an in-memory last-click attribution service. There are two event types: - click(timestamp, userId, campaignId) - conversion(times...
Find invalid transactions in time-sorted input
Problem You are given a list of transaction records, already sorted in non-decreasing order by time. Each transaction is a string in the form: "name,t...
Implement Calendar, Tokenizer, and Meeting Optimizer
Implement the following three coding tasks. 1. Calendar insertion check You are given a list of existing calendar events, where each event is a hal...
Implement Top-p (Nucleus) Sampling in NumPy
Implement top-p (nucleus) sampling for next-token selection in a language model, using only NumPy. Given a vector of raw logits over a vocabulary, top...
Schedule Non-Overlapping Meetings Efficiently
Implement a meeting scheduler that stores meetings as half-open intervals [start, end), where start and end are integer timestamps and start < end. Th...
Implement text editor with undo/redo
Implement a TextDocument class that supports applying edit operations, reading the current content, and full undo/redo, based on the following Python ...
Implement wildcard querySelector to extract URL
Problem: Extract a hidden URL from a deeply nested DOM A webpage hides a URL by splitting it into individual characters stored in DOM elements. The DO...
Write SQL using joins and window functions
SQL Coding: Rank within Groups with Joins You are given two tables: accounts - account_id (string) - customer_id (string) - segment (string) — e.g., "...