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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Compute Plant Infection Time
You are given an m x n grid representing a garden. Each cell is one of the following: - 0: empty ground - 1: a healthy plant - 2: an infected plant - ...
Fix a Corrupted Bootloader Instruction
You are given a bootloader program as a list of text instructions. Each instruction has an opcode and a signed integer value, such as plus +1 or jump ...
Find User Airport at a Time
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Solve Flower Placement and Directory Deletion
You will solve two independent coding tasks. Task 1: Place Flowers on a Grid Given an N x N grid: - 'H' represents a house. - '0' represents an empty ...
Calculate Driver Payments
Build a payout calculator for a delivery platform. You are given: - A list of delivery records. Each record has delivery_id, driver_id, start_time, en...
Minimize Circular Redistribution Cost
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Implement a Unique Lines Command
Implement a simplified version of the Unix uniq command. Given an input text file, output the file contents with consecutive duplicate lines collapsed...
Count Candies from Unlockable Boxes
You are given an object-oriented representation of boxes in a house. Initially, exactly one box is physically accessible. Each Box has: - A unique id....
Implement Event Filtering and Queue Routing
An upstream event pipeline continuously emits events as JSON strings. You need to implement an in-memory routing service that decides which downstream...
Implement an In-Memory File System
Implement an in-memory file system directory management tool. Your tool should support the following operations: 1. Create a file in a directory. 2. C...
Consolidate On-Call Rotation Segments
You are given an array of on-call rotation intervals. Each interval has the form: `text {name: string, start: int, end: int} ` Each interval is half-o...
Add One to Digit Array
You are given an array of decimal digits representing a non-negative integer. The most significant digit is at index 0, and the array contains no lead...
Implement a Database Connection Pool
Implement a simple database connection pool. You are given a mock database client with a function such as db.query(connection, sql) or an equivalent s...
Deep Equality of Two Records
Deep Equality of Two Records You are given two records (think of them as instances of a struct / class / nested object). Write a function that decides...
Implement Courier Delivery Cost Tracking
Design and implement a small in-memory cost-tracking service for food-delivery couriers. Each courier has a unique driverId and an hourlyRate. A deliv...
Implement stream queries and bounded-difference subarrays
Solve both coding tasks. Task 1: Track the first non-repeated number in a stream Design a data structure that supports a stream of integers. Implement...
Implement Layer History and Grid Counting
The coding portion of this loop covered two independent tasks. Implement each cleanly, handle the edge cases, and analyze the time and space complexit...
Design an in-memory banking system
Implement an in-memory banking system (e.g., in Java) that supports the following operations on user accounts. Assume user IDs are unique strings and ...
Find Maximum Eastbound City Visits and Parse CSV
Answer both coding questions. Question 1: Maximum eastbound city visits You are given two arrays of the same length: - cities[i]: the name of the i-th...
Find Shortest Unique Prefixes
Given a list of distinct non-empty words, return the shortest unique prefix for each word in the same order as the input. A prefix of a word is consid...