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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Solve four classic algorithm problems
You are given four independent coding tasks. For each task, implement the required function. --- Problem 1: Zigzag level-order traversal of a binary t...
Design a data structure to find streaming median
Problem Design a data structure that supports maintaining the median of a stream of integers. Implement a class/ADT with the following operations: - a...
Implement custom iterator classes
Question In a blank coding environment (no IDE assistance, no autocomplete), implement an iterator abstraction entirely from scratch. The interviewer ...
Implement toy-language types and generic substitution
Problem: Toy Language Type System (Printing + Generic Resolution) You are implementing a small type system for a custom “Toy Language”. Types can be: ...
Sort Three Categories In Place
You are given an array items containing only the values 0, 1, and 2, where each value represents a category. Rearrange the array in-place so that all ...
Schedule vector ops on heterogeneous cores
You are optimizing a “vectored computation” on a heterogeneous (non-SMP) CPU with asymmetric cores. Hardware model There are two core types: - D-cores...
Implement a type-based mutex for tasks
Problem You are given a multithreaded task runner. Each task has: - task_id: int - task_type: "gen" | "score" - duration: int (seconds) Each task runs...
Find the third-largest word by length
Given an array of strings strArr (length ≥ 3), return the third largest word when ranking words by string length in descending order. Ranking rules: -...
Group strings that are anagrams
Given an array of strings, group the strings into lists such that each list contains strings that are anagrams of each other. Definition Two strings a...
Evaluate piecewise linear function at x
You are given a polyline defined by n 2D points \((x_i, y_i)\). Connecting consecutive points with straight line segments forms a piecewise linear fun...
Count friend requests based on age rules
Problem You are given an array ages, where ages[i] is the age of the i-th person. A person of age A will send a friend request to a person of age B if...
Process document edit events
Implement a line-based document editor. You are given: - an initial document represented as an array of strings, where each string is one line - a lis...
Find first non-repeating character index
You are given two separate coding tasks. Task 1: First Unique Character Given a string s (lowercase/ASCII letters), return the index of the first char...
Compute shortest delivery route with dangerous stops
Delivery Route Planning With Dangerous Stops You are given delivery stops (nodes) and a set of routes. Each route is a list of stops, and you can trav...
Match readings with latest same-city humidity
Problem You are given two time-sorted lists of sensor readings: - Temperature records: (time, city, reading) - Humidity records: (time, city, reading)...
Build a FastAPI summarization service
Implement a minimal but production-ready FastAPI service for text summarization. Requirements: - Expose an endpoint POST /summarize. - The request bod...
Solve two linked list/array tasks
You are given two independent coding tasks. Task 1: Remove the N-th node from the end of a singly linked list Given the head of a singly linked list a...
Solve four design-leaning coding problems
You are given four independent interview-style coding tasks. For each task, implement the requested function/class with clear inputs/outputs and reaso...
Implement an extensible prefix tree
Implement a prefix tree (trie) supporting insert(word), search(word), startsWith(prefix), countPrefix(prefix), and erase(word). Optimize for time and ...
Determine Whether Queries Can Zero Array
You are given an integer array nums of length n and a list of range operations queries, where each query is of the form [l, r, val]. Process the queri...