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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Find missing rank in a straight
You are given a list of 4 distinct characters representing card ranks from a 5-card straight (5 consecutive ranks) with exactly one rank missing. Rank...
Design structure for bottom-K customers by revenue
This question evaluates data structure design and algorithmic complexity for dynamic order-statistics and update operations, focusing on maintaining c...
Compute Range Sum Quickly
This question evaluates a candidate's understanding of range-sum queries, array preprocessing techniques and algorithmic complexity for answering mult...
Solve three scheduling and array problems
In this round you are given three separate coding problems to solve. --- Problem 1: Schedule tasks with cooldown You are given: - A list of tasks, whe...
Implement stacks, streaming median, and upward path sum
Complete the following coding problems. State the time/space complexity and key edge cases for each. 1) MinStack Design a stack that supports: - push(...
Find Banks From Identifier Mappings
Plaid receives institution metadata from multiple sources. You are given two mappings: 1. code_to_institution: a one-to-one mapping from a bank code t...
Compute CDF from a PDF Function
This question evaluates a candidate's skills in numerical integration, applied numerical methods, and probability/statistics by requiring construction...
Implement prefix and suffix file search
Implement data structures and APIs to store file names and support efficient queries that match both a given prefix and suffix. Provide methods add(na...
Refactor rock–paper–scissors for config and ties
Refactor an existing Rock–Paper–Scissors tournament with three robot players so that the number of rounds is configurable and the system also tracks t...
Devise sequence-rule detection strategy
You are given an integer sequence with 2 ≤ n ≤ 50 terms, possibly following rules such as arithmetic/geometric progressions, alternating patterns, pol...
Implement KV store serialization
Implement serialization and deserialization for an in‑memory key‑value store to and from a contiguous bytes buffer. Keys are UTF‑8 strings; values may...
Design autocomplete with Trie
Design and implement an autocomplete service backed by a prefix tree (Trie). The service stores a dynamic dictionary of words, each carrying an intege...
Solve grid compromise spread with BFS
You are given an m×n grid representing a data center: 0 = empty rack, 1 = secure server, 2 = compromised server. Each minute, any secure server that i...
Traverse binary tree by levels with constraints
Given a binary tree and a predicate P(node), perform a level-by-level traversal that collects, for each level, only the nodes whose values satisfy P. ...
Determine task order with prerequisites
You are given n tasks labeled 0..n−1 and a list of prerequisite pairs (a, b) meaning task b must be completed before task a. Determine one valid order...
Find longest common contiguous subarray
Given two integer arrays A and B, find the length of the longest contiguous subarray that appears in both arrays. If multiple exist, return any one pa...
Solve a two-jug measuring problem
You are given two jugs with capacities x and y liters and an unlimited water source. You may perform these operations: fill a jug, empty a jug, or pou...
Determine Whether Courses Can Be Completed
You are given an integer numCourses, representing courses labeled from 0 to numCourses - 1, and a list prerequisites. Each prerequisite is a pair [cou...
Find a valid dependency order
You are given n tasks labeled from 0 to n - 1 and a list of dependency pairs dependencies, where each pair [a, b] means task b must be completed befor...
Solve classic coding interview problems
These problems evaluate algorithmic problem-solving skills including dynamic programming and combinatorics for the egg-dropping scenario, array manipu...