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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Solve path and inventory problems
The coding rounds contained two algorithmic exercises: 1. Maximum multiplier path You are given an m x n grid of integers. Start at the top-left ce...
Compute User Login Streaks
Given a table user_login_log with the following columns: - user_id: the user identifier - login_date: the calendar date of a login event A user may ha...
Simulate Plant Infection Spread
Given an m x n grid representing farmland: - 0 = empty cell - 1 = healthy plant - 2 = infected plant - 3 = obstacle Every minute, each infected plant ...
Find shortest word transformation with caching
You are given a start word and an end word of equal length, and a dictionary of valid words. In one move you may change exactly one letter to form a n...
Solve tree traversal and two-pointer problems
Implement the following independent problems: 1) Vertical columns: Given a binary tree, return lists of node values grouped by vertical columns from l...
Solve unique triplets summing to target
Implement a function that, given an integer array nums and an integer target T, returns all unique triplets [x, y, z] from nums such that x + y + z = ...
Implement a simple service with tests
You're given a short written specification for a small service class (no external dependencies). Implement the class using clear control flow (primari...
Find shortest substring with n unique letters
Problem You are given a string s consisting of lowercase English letters and an integer n (1 ≤ n ≤ 26). Find the length of the shortest contiguous sub...
Implement k-th largest in a number stream
You are designing a small library to monitor statistics over a stream of integers. Implement a data structure that, given an integer k and an initial ...
Search Book Titles
You are given a list of book titles and a user query string. Return all titles that are relevant to the query. A title is considered relevant if any t...
Find Business Degrees of Separation
Implement a feature for a small-business network. QuickBooks has data showing business relationships, such as one business regularly buying goods or s...
Solve substring and worker assignment
The interview included two algorithm problems: 1. Shortest covering substring: Given two strings s and t, return the shortest contiguous substring of ...
Simulate Plant Infection With Controlled Burning
You are given an R by C grid of plants. Each plant is initially healthy, infected, recovered, or dead. A plant has up to four orthogonal neighbors. De...
Validate Bracket Sequence
Given a string containing only the characters ()[]{}, determine whether the brackets are properly matched. A bracket string is considered valid if: - ...
Implement BFS and a Job Scheduler
The interview report described two coding questions: grid reveal with BFS and a concurrent periodic job scheduler. Constraints & Assumptions - For the...
Implement credit ledger with out-of-order timestamps
Problem You are implementing a GPU credit ledger that supports adding credits, charging credits, and querying balances. Requests can arrive in any tim...
Solve linked list, tree, and grid problems
Problem A — Find cycle entry in a singly linked list You are given the head of a singly linked list. The list may contain a cycle. - Return the node w...
Write a generator for substring pattern matches
Problem Write a generator that scans a string and emits a value whenever a substring matches a given pattern. Input - A string s - A string pattern (n...
Convert 32-bit integer to hexadecimal
Problem Given a 32-bit signed integer num, return its hexadecimal representation as a string. Requirements - Use lowercase letters a-f. - Do not inclu...
Find K Nearest Points
Given an array of 2D points points, where points[i] = [x_i, y_i], and an integer k, return any k points whose Euclidean distance to the origin (0, 0) ...