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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"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."
Solve Subarray Sum and Local Minimum
Two coding problems were reported in the same phone-screen round: 1. Count target-sum subarrays. Given an integer array nums and an integer k, return ...
Find the Extra Edge
You are given an undirected graph that started as a tree with n nodes labeled from 1 to n. One additional edge was then added between two different ex...
Validate abbreviations and brackets
The coding round included two short implementation problems: 1. Abbreviation validation Given a lowercase word word and a string abbr, determine wheth...
Implement Document Predicate APIs
Design a simple document service that stores text documents identified by filename. Implement these APIs: - InsertDoc(filename, content): store or ove...
Build a File-Backed Key-Value Store
Implement a persistent key-value store that supports the following operations for string keys and string values: - put(key, value) - get(key) - delete...
Find Dictionary Matches for a Jammed String
You are given: - a dictionary of lowercase words - an input string jammed_string A keyboard may be stuck, so when typing an original word, any charact...
Find the Critical Path
You are given a project represented as a directed acyclic graph of tasks. Each task has: - a unique task name - a list of prerequisite task names - a ...
Implement Task Dependencies and Failure
Implement a Python in-memory task manager for an AI workflow system. Each task has a unique task_id and a status. A task may depend on other tasks. If...
Find Fastest Commute Mode
You are given a 2D city grid containing: - S: starting location - D: destination - X: blocked cell that cannot be entered - 1, 2, 3, 4: cells usable b...
Search Monster Battle Strategies
You are given two teams of monsters. Each monster has: - hp: starting health - attack: damage dealt per attack - revive_hp: if greater than 0, the mon...
Design an In-Memory Database
Implement a simple in-memory database with a flexible, schema-less record model. Requirements: - Each record is a mapping from column_name to value. -...
Design O(1) Randomized Multiset
Implement a randomized multiset data structure that allows duplicate values and supports the following operations in average constant time: - insert(v...
Build Ranked Feed With Photo Batching
You are given a list of feed objects. Each object has: - id: a unique string - type: one of Normal, Video, or Photo - score: a numeric ranking score C...
Find Maximum Chain Activations
You are given n devices, where each device is represented as [x, y, r]. Device i is located at coordinates (x, y) and can directly activate device j i...
Implement Multi-Level In-Memory Services
Implement the following independent multi-level in-memory service simulations. In an interview, you may receive one scenario and unlock the levels seq...
Solve Knight and Reversal Problems
The online assessment contained two coding problems: 1. Generalized knight shortest path: Given an integer n, consider an n x n chessboard with coordi...
Find the Kth Largest in Two Sorted Arrays
You are given two arrays sorted in ascending order and an integer k. Return the kth largest element among all elements from both arrays combined. Coun...
Wrap Matching Substrings in Bold Tags
During a machine learning engineer phone screen, the coding task was: You are given a string text and a list of strings patterns. Return a new string ...
Implement Calendar Layout and String Packing
The interview reportedly included two separate coding exercises: 1. Day-view calendar layout - You are given a list of events for a single day. Eac...
Implement Sliding-Window Rate Limiter
You are asked to build an in-memory rate limiter for an API service. For each user_id, allow at most limit requests during any rolling window of windo...