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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Find Smallest Common Row Value
You are given a 2D integer matrix where each row is sorted in strictly increasing order. Return the smallest integer that appears in every row. If no ...
Determine Whether a Word Transformation Exists
Given a beginWord, an endWord, and a list of valid words wordList, determine whether it is possible to transform beginWord into endWord. Rules: - Each...
Determine if tree has path sum
Problem Given the root of a binary tree and an integer targetSum, return true if the tree has a root-to-leaf path such that adding up all the values a...
Solve stock profit and vertical tree traversal
You have a 60-minute coding interview with two algorithm questions: 1) Max profit from one stock trade - Input: an integer array prices, where prices[...
Solve mixed coding tasks from interviews
Solve the following interview-style coding problems (you may choose any programming language unless specified). Provide correct logic and handle edge ...
Solve delimiter and CSV tasks
The interview included two coding tasks: 1. Validate bracket sequences. Given a string consisting only of the characters (, ), [, ], {, and }, determi...
Build a concurrent web crawler
Implement a web crawler that starts from a given URL and visits every reachable page on the same host. You are given: - start_url: a string representi...
Compute tree depth and meeting rooms
Solve both coding problems. Problem 1: Maximum depth of a binary tree Given the root of a binary tree, return its maximum depth. The maximum depth is ...
Design body camera checkout system
You are building an in-memory checkout system for police body cameras. The system is initialized with a set of unique camera IDs. Each officer can hol...
Find first 5-7-5 haiku in sentence
Question Given a sentence containing mixed case and punctuation, and a syllable dictionary mapping lowercase words to their syllable counts, implement...
Implement Optimal Bucket Batching
You are given an array lengths of K document lengths and an integer G representing the number of available GPUs. A batch is assigned to one GPU, and e...
Implement four coding challenges
You are asked to solve the following four independent coding problems. --- 1) Block Placement Simulator (Tetris-like) You have an empty n x m grid (ro...
Maximize Unique Letters
Given a list of lowercase words, choose any subset of words such that: - no selected word contains a repeated character internally, and - no character...
Design refundable transaction ledger and prioritization rules
Design and implement a transaction ledger that ingests a stream of records where each record is either a payment or a refund. Each payment has {id, us...
Solve string and hashmap interview tasks
Coding questions (solve both) 1) First non-repeating character Given a string s, return the first character that appears exactly once in the string. -...
Implement an LRU cache with follow-ups
Coding: Implement an LRU Cache and discuss concurrency Design and implement an in-memory Least Recently Used (LRU) cache data structure. The cache sho...
Find maximum value in huge text file
You are given the path to a very large text file on disk. The file has the following properties: - Each line contains exactly one signed 64-bit intege...
Implement ad filtering and concurrent cache
Two coding tasks were described. 1. Ad candidate filtering: You are given a list of ad candidates. Each ad has ad_id, company, topic, and score. Retur...
Swap kth-from-end node with head
Given the head of a singly linked list and an integer k, swap the k-th node from the end with the head node, using O(1) extra memory. Requirements: - ...
Serialize Expression Tree Minimizing Parentheses
Given a binary expression syntax tree, serialize it into an infix string using the minimum number of parentheses required to preserve the tree's evalu...