Coding & Algorithms Interview Questions
Practice 2,960 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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Return all valid word-break sentences
Given a string s and a dictionary of strings wordDict, insert spaces into s to form a sentence such that every token is in wordDict. Return all possib...
Answer common graph, grid, and array tasks
Problem 1: Largest continuous island after filling sea (1D) Humans can convert ocean cells into land by filling them. Input - islands: a 1D array of l...
Minimize operations to reduce integer to zero
You are given a non-negative integer n. In one operation: - If n is even, you may replace n with n / 2. - If n is odd, you may replace n with either n...
Solve Two Array Optimization Problems
This online assessment included two coding problems. Problem 1: Maximize protected city population You are given: - an integer n - an array population...
Evaluate Arithmetic Expressions
Implement a function that evaluates a string arithmetic expression. Base problem: - The input is a string s containing non-negative integers, spaces, ...
Solve sliding-window, flattening, decode, and O(1) random set
You are given four independent coding tasks. For each, describe your approach, time complexity, and handle edge cases. 1) Longest substring without re...
Implement Recipe Storage CRUD
Implement an in-memory RecipeStore that supports CRUD operations for recipes. Each recipe contains: - id: a string identifier in the form recipe<n> - ...
Compute unique-dasher concurrency with tie-breaking
You are given N delivery assignments, each as (dasherId, startTime, endTime) with 0 <= startTime < endTime. A single dasher may hold multiple overlapp...
Implement a single-producer multi-consumer ring buffer
Implement a fixed-capacity ring buffer in C++ for a setting with one producer and multiple consumers. Design a class that stores integers in a preallo...
Predict most likely next word from training data
You are given tokenized training data consisting of multiple sentences (each sentence is a list of words). Build a lightweight model/data structure th...
Solve interval, grid-fill, and heap tasks
You are asked to solve the following algorithmic problems. Problem 1: Concurrent users from online intervals You are given n inclusive time intervals ...
Maximize distinct values after unique ± offsets
Problem You are given an integer array a of length n and a non-negative integer k. For each index i, you must choose: - an integer offset d_i such tha...
Remove adjacent duplicates and handle tree input
You are asked three related coding questions. 1) Remove adjacent duplicates (repeatedly) Given a string s (lowercase English letters), repeatedly remo...
Implement an event emitter
Implement an EventEmitter class for a frontend environment. The class should support these methods: - on(eventName, listener): register a listener fun...
Compute Remaining GPUs With Switching Limits
Suppose you manage n GPU clusters with fixed daily capacities capacity[i]. Each day starts fresh with the full capacity, because all GPUs are returned...
Implement follow graph with snapshots and recommendations
Design and implement an in-memory “social network” component that supports following/unfollowing, point-in-time (snapshot) queries, and a simple recom...
Design autocomplete with Trie
Design and implement an autocomplete service using a prefix tree (Trie). Support operations insert(word, weight), update(word, newWeight), delete(word...
Delete a Character From Cover
You are given a source string book and a cipher represented by a list of inclusive index intervals cover = [(l1, r1), ..., (lm, rm)]. The decoded ciph...
Debug Queues and Solve Arrays
During the coding rounds, the interviewer asked several implementation problems: 1. Debug a priority queue. You are given an array-backed min-heap. Th...
Can You Reach the Last Index?
You are given an array nums of non-negative integers. You start at index 0. From index i, you may jump to any index j such that i < j <= i + nums[i]. ...