Coding & Algorithms Interview Questions
Practice 3,429 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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Design robot path boundedness with repeats
You are given a 2D grid with a set of blocked cells (obstacles) and a robot starting at (0, 0) facing north. The robot executes a finite instruction s...
Implement Connect Four with win detection
Implement a Connect Four game engine. Support a general m×n board (default 6× 7) and a win condition of k in a row (default 4). Provide an API: Connec...
Compute shortest path to collect all keys
You are given an m×n grid containing walls (#), open cells (.), a single start cell (@), up to six keys labeled 'a'–'f', and matching doors 'A'–'F' th...
Find palindrome-forming string pairs
Given an array of distinct lowercase strings words, return all index pairs (i, j) with i != j such that the concatenation words[i] + words[j] is a pal...
Merge two sorted linked lists
Given the heads of two singly linked lists sorted in non-decreasing order, merge them into a single sorted singly linked list and return its head. Imp...
Find nearest common manager for multiple employees
Given an organizational hierarchy modeled as a rooted tree, build the tree from (employee, manager) pairs and implement a function that, for k ≥ 2 emp...
Implement version string comparator with extensions
Implement a function compareVersions(a, b) that compares two software version strings. Each version consists of dot-separated numeric components (e.g....
Find substring from dictionary concatenation
Given a string s and a dictionary of words dict, determine whether s contains a substring that is exactly a concatenation of one or more words from di...
Compute fruit spoilage time in a grid
Given an m×n grid representing kitchen cells: 0 for empty, 1 for fresh fruit, and 2 for spoiled fruit. Each minute, any fresh fruit adjacent (up, down...
Implement file word count
Write a function that reads a large text file and returns the frequency count of each word. Define how you will normalize tokens (case, Unicode, punct...
Determine feasible task ordering
You are given n tasks labeled 0..n−1 and a list of dependency pairs (a, b) meaning task a requires task b to be completed first. Implement functions t...
Implement island counting with BFS and DFS
Question You are given an m x n grid of characters where '1' represents land and '0' represents water. Count the number of distinct islands (connected...
Solve BFS grid delivery routing
You are given an m×n grid representing a city: 'S' are DashMart stores, 'H' are homes, '.' are roads, and '#' are obstacles. Movement is allowed in fo...
Implement string matching with follow-up
Question Given a text T and a pattern P, implement a function firstIndex(T, P) that returns the starting index of the first occurrence of P in T, or -...
Compute and optimize average wait time
You are given n pickup orders for a grocery delivery counter. Each order i is described by orders[i] = [arrival_i, service_i] in minutes, where arriva...
Check diagonal equality in a matrix
Given an m x n integer matrix, determine whether every top-left to bottom-right diagonal contains identical values (all elements along each such diago...
Design an IP filter using CIDR rules
Explain CIDR notation with a couple of concrete examples. Show how to convert a prefix like 192.168.0.0/16 into an inclusive 32-bit integer range and ...
Implement basic calculator
Question LeetCode 227. Basic Calculator II – implement an arithmetic expression evaluator supporting +, -, *, / and integer operands https://leetcode....
Implement tree ops and LRU cache
Question Implement set(index) and clear(index) for the leaves of a full binary tree initially filled with 0s, where a parent node becomes 1 only when ...
Review Python geodata code
Question You are given a Python codebase that performs geolocation data processing. Conduct a thorough code review: identify readability, correctness,...