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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Support updates and count target-sum pairs
You are given two integer arrays: - A (fixed / primary) - B (modifiable / secondary) You must process a sequence of operations of two types: 1. Update...
Solve meeting-room scheduling and shortest paths
You are asked to solve two algorithmic problems. Part A: Meeting-room scheduling (intervals) You are given an array of meeting time intervals interval...
Find viewing direction that sees most points
You are standing at the origin on a 2D plane. You are given a list of points points[i] = (xi, yi) (not necessarily distinct), and a viewing angle thet...
Solve several streaming, DAG, and DP tasks
You were asked multiple algorithmic questions. 1) Streaming longest subarray with average S You receive an infinite stream of integers (can be positiv...
Write Transaction Analytics SQL Queries
You are given a credit-card transaction dataset with the following tables. transactions | column | type | description | |---|---|---| | transaction_id...
Implement Notification Rate Limiter
Implement should_send_notifications(user_id, timestamp) -> bool. You are given two mappings: - each user_id belongs to exactly one team_id - each team...
Implement paginated retrieval of transactions
Given a large list of transaction records (id, userId, amount, createdAt), implement APIs to return transactions in reverse chronological order with p...
Return a valid course completion order
You are given an integer n representing n courses labeled 0..n-1 and a list of prerequisite pairs prerequisites, where each pair [a, b] means you must...
Find Earliest Full Connectivity Timestamp
You are given: - A list of all user IDs in a ride-sharing system. - A chronological text log of ride-sharing events. Each relevant event contains a ti...
Implement stateful connection router simulator
You are implementing a simplified connection router / load balancer for a Jupyter-like multi-tenant server system. There are N target servers, indexed...
Sample a string by real-valued scores
You are given: - A list of strings texts (e.g., user comments), length n. - A list of floating-point scores scores of length n, where each score can b...
Validate whether a given sequence is a Hamiltonian path
You are given strArr, an array of three strings describing an undirected graph and a proposed vertex visit order: 1. strArr[0]: a comma-separated list...
Extend a Maze Solver
You are given an existing Python maze solver and a suite of unit tests. The maze is a 2D grid that uses # for walls, . for open cells, S for the start...
Implement follow graph with snapshots
Problem You are building an in-memory social network relationship store that supports time-travel queries. Users are identified by integers. A directe...
Compute worst-case guesses for adaptive hangman
You are given a set of distinct lowercase words, all of the same length. A hidden word is chosen from this set, but the host is adversarial: after eac...
Solve Three Algorithm Variants
You are given three independent coding problems. For each one, describe and implement an efficient solution. 1. Generate queue arrangements - You a...
Find the Next Larger Palindrome
Given a positive integer n, return the smallest integer strictly greater than n whose decimal representation is a palindrome. A palindrome reads the s...
Implement a DAG task graph
Implement a class TaskGraph to represent a directed acyclic graph of tasks. Support these operations: 1. add_task(task_id: str) -> None: Add a task if...
Compute minimum time with task cooldowns
You are given a multiset of task types represented by uppercase letters (e.g., A, A, A, B, B, C). Each task takes exactly 1 time unit to execute. Runn...
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...