Coding & Algorithms Interview Questions
Practice 3,469 real Coding & Algorithms interview questions for 2026. Covers companies like Meta, Amazon, Google, Uber, and Microsoft. Real questions from actual interviews with detailed solutions — ideal for focused interview preparation. Coding & Algorithms interview questions are the single most common technical gate for software engineering roles and are used to evaluate problem framing, algorithm selection, complexity trade-offs, correctness, edge-case reasoning, and clear communication under time pressure. Expect this category to appear in early technical screens and repeatedly across onsite loops at companies that weight it heavily (notably Meta, Google, and Amazon). Interviews will test arrays and strings, trees and graphs, dynamic programming, hashing and two‑pointer techniques, and the candidate’s ability to test and optimize code in a shared editor. Prepare with timed mock interviews, practice in the same editor you’ll use live, and build a progressive schedule that moves from fundamentals to medium/hard problems; typical candidates invest several weeks to a few months of focused practice depending on seniority and target company.
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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."
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Solve four algorithm design tasks
Solve the following four algorithmic tasks: 1) Implement wildcard pattern matcher: Given a text s and a pattern p where '?' matches any single charact...
Find value on most distinct levels
Given a binary tree whose nodes store values (e.g., characters), find the value that appears on the greatest number of distinct depth levels. For exam...
Design an Elevator System and Scheduler
Design an object-oriented elevator system. Define core classes and interfaces (elevator, controller, request, floor, buttons, sensors) and their inter...
Implement stack and interval algorithms with tests
Implement three coding tasks and design your own unit tests for each. 1) Validate Bracket String with a Stack - Input: a string s containing only '(',...
Solve and extend the Knapsack problem
You are given n items, each with an integer weight and value, and a knapsack capacity W. Implement 0/1 Knapsack to return the maximum total value and ...
Validate a simplified numeric string
Implement isValidNumber (s) that returns true if and only if the ASCII string s represents a valid number under these simplified rules: - Optional lea...
Design two-user communications handler with exceptions
Implement a two-user communications handler. Create: (A) CommsHandler(CommsHandlerABC) with methods connect(self, user1: Caller, user2: Caller) -> str...
Check strings against dictionary efficiently
Given a large dictionary of unique words and a list of query strings, return for each query whether it exists in the dictionary. The dictionary may co...
Implement text formatter and sum subarray products
1) Text formatter (LC-inspired variant): Given an array of words and an integer maxWidth W >= 1, break the words into lines so that the total length o...
Design an efficient Tic-Tac-Toe engine
Design a Tic-Tac-Toe engine on an n x n board. Implement move(row, col, player) -> result where result indicates no winner, player1 wins, player2 wins...
Convert number words to integer
Given a line containing an English phrase representing a number in the range −999,999,999 to 999,999,999, convert it to its integer value. Supported w...
Solve matrix components, median, and traversals
1) Binary matrix component: Given an m x n grid of 0s (background) and 1s (objects), return the size of the largest connected component where connecti...
Implement BFS shortest paths with reconstruction
Given an unweighted graph with n vertices and m edges represented as an adjacency list, implement breadth-first search (BFS) from a source vertex s to...
Simulate a two-player card war game
Simulate a two-player card war game Implement a function to simulate a two-player card game. Each player has a queue of card ranks (top at index 0), w...
Select maximum tasks before deadlines
Select maximum tasks before deadlines You are given a set of tasks, each with a positive duration and a deadline (lastDay). You may schedule tasks in ...
Maximize stock profit with constraints
Maximize stock profit with constraints Given an array prices of daily stock prices, you may make at most two complete transactions (buy then sell). Af...
Compute shortest path with obstacles
Compute shortest path with obstacles You are given an m×n grid with nonnegative cell costs and blocked cells marked '#'. You may move up, down, left, ...
Design a hierarchical locking tree
Design a hierarchical locking tree Design a LockingHierarchy data structure over a rooted tree of N nodes labeled 0..N-1, initialized with an integer ...
Find longest unique substring
Find longest unique substring Given a string s, find the length and one example of the longest substring of s that contains no repeated characters. If...
Count subarrays equal to target
Count subarrays equal to target Given an integer array nums and an integer k, count the number of contiguous subarrays whose sum equals k. Solve it in...