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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"Discovered PracHub 10 days before my interview. By day 5, I stopped being nervous. By interview day, I was actually excited to show what I knew."

"I recently cleared Uber interviews (strong hire in the design round) and all the questions were present in prachub."
"The search is what sold me. I typed in a really niche DP problem I got asked last year and it actually came up, full breakdown and everything. These guys are clearly updating it constantly."
Compute the next lexicographic permutation
Problem Given an integer array nums representing a permutation of its elements, modify the array in-place to produce the next lexicographically greate...
Compute max reachable cells per threshold
You are given: - An m x n integer matrix terrain. - An integer array limits of length k. For each query value L = limits[i], you start at the top-left...
Check pivot after removing one element
You are given an integer array nums (values may repeat and may be negative). You must remove exactly one element (remove one index). The remaining ele...
Measure 45 minutes with two ropes
You have two ropes. Each rope takes exactly 60 minutes to burn completely, but each rope burns at a non-uniform rate (some parts burn faster than othe...
Group duplicate files by content
Problem You are given a list of files in a filesystem. Each file has: - a full path (string) - a file size in bytes (integer) - file contents (concept...
Solve common string/tree/grid interview tasks
Problem Set (solve all in one interview) 1) Parse an integer from a string ("atoi"-style) Implement a function: - parseInt(s: string) -> int Given a s...
Parse code into operation triads IR
Problem: Operation-Triads Parsing (Mini Language) You are given a small, line-based programming language consisting of assignment statements and non-n...
Maximize protected population and bitwise AND
You are given two independent coding problems. Problem 1: Maximize protected population after moving units There are n cities in a line (indexed 1..n)...
Implement frequency + distance top‑K queries
You will implement solutions for two coding interview questions. Question 1: Return the top‑K points by frequency (with distance tie‑break) You are gi...
Solve frequency and tree-completeness problems
Problem A: Return the k most frequent values You are given an integer array nums and an integer k. Task: Return the k distinct values that occur most ...
Implement bitmap-based block allocator
Problem 1: Bitmap-based block allocator (OOD/coding) You are implementing a simple block allocator backed by a bitmap. - There are M blocks, indexed 0...
Solve common string/DP/stack problems
You are given four independent coding tasks. For each task, describe your approach and analyze time and space complexity. Task 1: Longest substring wi...
Parallelize chunked file download and verify integrity
You are implementing a simplified s3 sync-style download for a large remote object. A file is stored remotely as N fixed-size chunks (except possibly ...
Min deletions to avoid overlap in first k
You are given two integer arrays list1 and list2 and an integer k. You may delete elements from list2 (deletions can be at any positions). The relativ...
Compute board-game score from regions
You are given a 2D board for a board game. Each cell is encoded like G1 or W0: - The first character is the terrain/area type (e.g., G, W, S). - The d...
Compute BBO and NBBO from order data
You are given a list data of order records. Each record is a 4-tuple: ` (exchange_id, price, quantity, order_type) ` - exchange_id: string/int identif...
Minimize Increments to Equalize Path Costs
You are given a perfect binary tree with n nodes, labeled from 1 to n in level-order. For any non-leaf node i, its left child is 2 i and its right ch...
Implement BFS-based maze solver
Maze Printing and BFS Solver You are given a 2D grid representing a maze. Each cell of the grid is one of: - '#' – wall (cannot be passed) - '.' – emp...
Validate a bracket string
Problem Given a string s consisting only of the characters (, ), [, ], {, }, determine whether the string is valid. A string is valid if: 1. Every ope...
Decode an anagram sentence using vocabulary constraints
You are given: - vocab: a list of lowercase words (the "dictionary") - s: a string containing space-separated scrambled words Each scrambled word in s...