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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Maximize optional tasks under daily limit
You are given an integer limit and two integer arrays required and optional of length n. For each day i, you must schedule required[i]. If time remain...
Design a queue and analyze tradeoffs
Design a FIFO queue data structure that supports enqueue, dequeue, peek, and isEmpty. Compare implementations using a singly linked list, a dynamic ar...
Design a rolling five-minute hit counter
Design an in-memory hit counter that supports: ( 1) recordHit(timestamp) to log an event, and ( 2) getCountLast5Minutes(now) to return the number of e...
Implement power and balance-parentheses algorithms
Design and implement two algorithms: 1) Fast exponentiation: Implement a function pow(x, n) that returns a real number x raised to an integer exponent...
Implement a tennis score tracker
Design and implement a tennis game scoring function. Input: a stream of points won by players 'A' or 'B' (e.g., A, B, B, B, B). After each point, outp...
Debug and Fix Failing Unit Tests in Java
You receive a small Java project for a credit-card rewards service with three failing unit tests: calculatesTriplePointsForRestaurants, returnsUnknown...
Compute build order from dependencies
Given a set of package build dependencies, output a valid build order so that each package is built only after all of its dependencies. The input is a...
Implement a Simulated Memory Allocator
Implement a simulated memory allocator that supports allocate(size) and free(ptr) operations analogous to malloc and free. Treat memory as a contiguou...
Compute community ranges and town idle hours
You are given two in-memory datasets for a party-planning app. 1) PartyWindow: {partyId: string, startTime: ISO-8601 UTC datetime, endTime: ISO-8601 U...
Compute delivery times on a grid
You are given a 2D grid with cells marked as 'M' (warehouses), 'C' (customers), 'X' (obstacles), and '.' (roads). You can move up, down, left, or righ...
Implement sampling and subarray algorithms
This coding round contained two algorithmic prompts: uniform sampling in a 2D square and longest increasing contiguous subarray. Constraints & Assumpt...
Write SQL and merge linked lists
The technical interview included two coding-style tasks: a SQL analytics query and merging two sorted linked lists. Constraints & Assumptions - For SQ...
Implement a Timed Task Scheduler
Implement a runnable task scheduler. The scheduler should allow clients to add new tasks at any time. Each task has: - A callback or function to execu...
Find missing number from concatenated digits
Given an integer n (1 ≤ n ≤ 99) and a digit string s formed by concatenating the decimal representations of the integers 1..n except for one missing n...
Evaluate expression without stack, constant space
Question Given a string s representing a valid arithmetic expression of non-negative integers, the operators +, -, `, /, and spaces (there are no pare...
Explain algorithm strategies and complexity
You are faced with a complex, potentially ambiguous coding problem. Describe how you would clarify requirements, identify constraints, propose multipl...
Determine if robot path is bounded
A robot starts at (0, 0) facing North on an infinite grid. It executes a string s consisting of 'G' (move forward 1 unit), 'L' (turn left 90°), and 'R...
Compute sum of minima with removals
You are given an array weights[0..n-1] of positive integers representing product weights in a line. Repeat until no products remain: choose the lighte...
Compute Max Score From Up to 3 Categories
You are implementing a scoring function for a library summer reading program. Each book a student read is represented as a tuple (category: str, point...
Maximize Profit From Cutting Rods
Given an array lengths where lengths[i] is the length of the i-th rod, determine the maximum profit obtainable by choosing a single integer saleLength...