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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Assign bookings to minimum tennis courts
You are given a list of tennis court bookings. Each booking has a start time and an end time. Task Return an assignment plan that: 1. Assigns each boo...
Compute moving and weighted averages from a stream
You are processing a stream of numeric events (e.g., user activity counts). You are given a fixed window size X. Part 1: Moving average over last X va...
Find k-th smallest subarray sum
Problem You are given an integer array nums of length n where all elements are positive integers, and an integer k. Consider all non-empty contiguous ...
Maximize profit from one stock trade
Problem You are given an integer array prices where prices[i] is the price of a stock on day i. You may complete at most one transaction: choose a day...
Validate JSON against a protobuf-like schema
You are given a simplified protobuf-like schema definition and a JSON value. Determine whether the JSON conforms to the schema. Schema model - A schem...
Find earliest time all riders become connected
You are given activity logs for a ride-sharing app. Each log entry indicates that two riders shared a ride at a certain time, which creates an undirec...
Implement a traffic-light UI with JS
Frontend Coding: Traffic Light Build a simple traffic light component using HTML + CSS + JavaScript. Requirements - Render a vertical traffic light wi...
Find top-5 most similar rows across datasets
You are given two datasets with the same feature columns: - source (rows you want to match): - source_id (STRING/INT) - f1...fk (NUMERIC; may cont...
Solve queue switch and coin change puzzles
This entry contains two separate interview-style quantitative/algorithmic questions. --- 1. Queue switching decision problem You are standing in a sin...
Design cache with least-recently-used eviction
You are asked to design an in-memory key–value cache that supports a least-recently-used (LRU) eviction policy. The cache must support the following o...
Optimize invites under capacity constraints
You have n donors (n up to 100,000). For each donor i you know: p_online[i] (probability of donating if emailed), a_online[i] (expected donation condi...
Compute precision–recall curve on imbalanced data
You receive a CSV with columns: actual_label ∈ {0,1} and predicted_prob ∈ [0,1]; the positive class rate is ≈5%. a) Which evaluation metrics would you...
Implement lazy unique-merge generator for sorted streams
Write a Python generator merge_unique(a, b) that lazily merges two nondecreasing iterables a and b (potentially infinite) into a single nondecreasing ...
Implement max profit with K transactions (DP)
Given an array prices[0..n-1] of daily stock prices and an integer k, implement a bottom-up dynamic program to compute the maximum achievable profit w...
Implement streaming autocomplete under tight memory
Build an autocomplete service: Input: a list of up to 5,000,000 UTF-8 words (may include accents and hyphens), each with an integer popularity score t...
Compute array modes with ties and no-mode rule
Write a function that returns the mode(s) of an integer array. Requirements: if all values are unique, return an empty list (there is no mode); allow ...
Write mini-batch gradient descent
Implement a generic mini-batch gradient descent routine: inputs are differentiable loss L(θ; x), initial θ0, batch size b, steps T, and learning-rate ...
Optimize assembly-line scheduling with changeovers
You are scheduling a simplified car-assembly line with two parallel stations S1 and S2. Each job must be processed on exactly one station, processing ...
Implement min, mean, median robustly
Implement three functions in Python without using numpy/pandas: (1) my_min(nums) returning the minimum in O(n) time and O(1) space; (2) my_mean(nums) ...
Design airport dispatch with ETA uncertainty
You control airport pickups with streaming ETAs for arriving flights and live driver locations/queues. Design an online dispatch algorithm that minimi...