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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Merge overlapping time intervals
Problem: Merge Intervals You are given an array of intervals intervals, where each interval is a pair [start, end] with start <= end. Merge all overla...
Find maximum collinear points
Given a list of 2D points with integer coordinates, return the maximum number of points that lie on the same straight line. Input - points: a list of ...
Explore an HTTP Maze
You are given an HTTP API that represents a maze-like forest. The entrance is available at GET /mirkwood. Each location in the forest is identified by...
Simulate robot moves on a grid
You are given an m x n grid and a robot that starts at position (r, c) (0-indexed). You are also given a string commands consisting of characters 'U',...
Solve Two OA Algorithm Problems
The post describes two separate coding questions from an online assessment: 1. Greedy deletion by minimum value Given an integer array nums, repeate...
Count All-One Square Submatrices
Given an n x n binary matrix, count how many square submatrices contain only 1s. A square submatrix can have any side length from 1 to n. Example: `te...
Solve Tree Diameter and Palindromic Counts
You will be given two independent coding problems. For each problem, explain your approach clearly and analyze both time and space complexity. Problem...
Sort a nearly sorted array
Given an array of length \(n\) in which every element is at most \(k\) positions away from its location in the fully sorted order, design an algorithm...
Generate Account Email Notifications
You are building an email notification scheduler for user accounts. You are given: 1. A list of user accounts. Each account has: - account_id - ...
Convert State Stream to Events
You are given an array states where states[i] is the categorical output of a monitoring function at timestamp i. Consecutive equal values belong to th...
Write SQL for app metrics
You are given a simplified schema for a photo-sharing app: - users(user_id, user_name, joined_at) - photos(photo_id, user_id, created_at) - follows(fo...
Convert IPv4 Ranges to CIDR Blocks
Implement a function that summarizes a consecutive IPv4 address range using the smallest possible list of CIDR blocks. You are given: - start_ip: a va...
Design a violation log analyzer
You are given an append-only list of violation events as tuples (id: string, policy: string, date: ISO-8601 string). Build an in-memory "Violation Log...
Implement an LRU Cache
Problem Design and implement an LRU (Least Recently Used) Cache that supports the following operations in O(1) average time: - get(key): - Return th...
Find longest subsequence of x that is a substring of y
Given two strings x and y, compute the maximum length of a string s such that: - s is a subsequence of x (can delete zero or more characters from x wi...
Find Maximum Island Perimeter
You are given an m x n binary grid where 1 represents land and 0 represents water. An island is a group of land cells connected vertically or horizont...
Find possible robot positions
You are given a 2D grid where '.' represents an open cell and '#' represents a wall. A hidden robot is standing on one open cell. The robot's sensor r...
Optimize CUDA GEMM with tiling and coalescing
CUDA Execution Model, Memory Hierarchy, and GEMM Kernel Design Part 1: Concepts Explain: - CUDA execution model: grid, blocks, warps, threads (SIMT). ...
Compute CDF from a PDF Function
You are given a callable function pdf(t) that returns the probability density of a normal distribution at value t. Implement a function cdf(x) that re...
Implement Checksums and Feature Rollout Evaluation
Complete the following two coding tasks in a 90-minute online assessment. An AI coding assistant may be available, but the submitted code must pass th...