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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Implement an in-memory key-field-value DB with TTL
In-Memory DB with TTL + Scan + Backup/Restore Implement an in-memory database storing records by (key, field) -> value with optional TTL. Data model /...
Find minimum moves to solve the 15-puzzle
Problem Given a 4×4 sliding puzzle (the classic 15-puzzle), compute the minimum number of moves required to reach the solved state, or return -1 if it...
Solve Decimal Coin Change
Given a list of coin denominations represented as decimal values and a target amount represented as a decimal value, return the minimum number of coin...
Find robots matching obstacle-distance signature
You are given a 2D grid and a distance signature dist = [left, top, bottom, right]. Grid Each cell is one of: - O : a robot - E : empty - X : obstacle...
Solve Two Sorted-Array Tasks
Implement solutions for the following two array problems: 1. Sorted values, return sorted squares You are given an integer array sorted in non-de...
Solve common string and subarray problems
You are given three coding tasks: 1) Reverse a string - Input: a string s. - Output: the string with characters in reverse order. 2) Maximum sum of a ...
Implement a multi-level digital recipe manager
Implement a RecipeManager class for a digital recipe manager. The task is progressive (Levels 1–4). You can assume a single-process in-memory implemen...
Find pairs with the minimum absolute difference
Given an integer array (not necessarily sorted), find the minimum absolute difference between any two distinct elements. Return all pairs of values th...
Implement exponentiation and fill grid distances
You are given two separate coding tasks. Task 1: Implement fast exponentiation Implement a function pow(x, n) that returns \(x^n\). - Input: - x: a ...
Merge Weekly Time Intervals
You are given a list of time intervals within a single week. Each time is written as a day-of-week plus a 24-hour clock, for example Sat 13:00 or Mon ...
Compute Courier Delivery Pay
A delivery platform has a service that can return all orders delivered by a courier. You are given: - courierId: the courier's identifier. - ratePerMi...
Solve Shortest Paths and Rental Allocation
You are given two independent coding problems. Problem 1: Shortest path in a weighted graph You are given a weighted graph where each edge has a non-n...
Write SQL for basic user metrics
You are given a simplified schema for a fictional social app called Nextagram: - users(user_id PK, username, created_at TIMESTAMP) - follows(follower_...
Solve Three Coding Problems
The interview included three coding problems: 1. Streaming top-k class. Design a class for an integer stream with a fixed parameter k. It should suppo...
Merge two sorted arrays in-place
Given two arrays arr1 and arr2, both sorted in ascending order. - Modify arr1 in-place to contain all elements from arr1 and arr2 in ascending order. ...
Implement polynomial multiplication API in C
Problem Implement an API in C to multiply two polynomials. A polynomial is represented by its coefficients. You must define the input and output forma...
Implement File Tail and Sensor Health
This interview included two coding tasks. 1. Print the last N lines of a file You are given a very large newline-delimited text file and a limited ...
Return a Package Build Order
You are given an API: `python get_dependencies(package) -> list[str] ` It returns the direct dependencies of a given package. If package A depends on ...
Implement integer division without using division
You are given two 32-bit signed integers dividend and divisor. Implement a function that divides dividend by divisor and returns the integer quotient,...
Process multi-currency payments with fees
You are building a small payment processor for a multi-currency wallet. Inputs 1. Wallet balances: a map balances[currency] -> integer representing th...