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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Compute sliding window median
Question LeetCode 480. Sliding Window Median: Given an array nums and an integer k, find the median of each sliding window of size k as the window mov...
Process auth requests with fraud rules
Question Implement a function that, given a list of Authorization Requests (timestamp_seconds, unique_id, amount, card_number, merchant), outputs a hu...
Choose container set to minimize waste
Question A pharmaceutical company is packaging liquid medicine for shipment. Each customer order has a required volume. The company can choose exactly...
Implement a Flappy Bird Jump Agent
This question evaluates discrete-time physics simulation, real-time decision-making under constraints, collision detection, and deterministic control-...
Design a Balloon Festival Simulator
Implement a class BalloonFestival with the following API and rules. Goal Track hot air balloons (yours and competitors), evolving wind fields, and bal...
Implement node messaging and path discovery
You have a network where each node knows only its parent and its children and can send messages to its parent and children. 1) Implement a sendMessage...
Compute interval mode, BST range sum, exclusive time
You are given several independent coding tasks. A) Most frequent integer covered by intervals You are given an integer range [-M, M] and a list of inc...
Find Kth Unique Maximum
This question evaluates algorithmic problem-solving skills related to sorted arrays, deduplication, and order-statistics across combined datasets, mea...
Design a Driver Payroll System
This question evaluates a candidate's understanding of data structure design, time-series aggregation, and algorithmic complexity for in-memory accoun...
Detect recurring transactions from a ledger
You are given a list of credit/debit card transactions. Each transaction has: - transaction_date (YYYY-MM-DD) - merchant (string) - amount (decimal, p...
Find first non-repeating character index
You are given two separate coding tasks. Task 1: First Unique Character Given a string s (lowercase/ASCII letters), return the index of the first char...
Find a secret word via match feedback
Word Guessing Game (Mastermind-style) You are given a list of unique candidate words wordlist. All words have the same length L and contain only lower...
Count friend requests based on age rules
Problem You are given an array ages, where ages[i] is the age of the i-th person. A person of age A will send a friend request to a person of age B if...
Implement K-means and solve interval/frequency tasks
Task 1 — Describe/implement K-means clustering Given: - A data matrix X with shape (n_samples, d). - An integer k (number of clusters). Explain (or wr...
Compute nested depth sum and grid distance
Problem A: Weighted sum of integers in a nested list You are given a nested list structure that may contain integers or other nested lists. Define the...
Implement ad matching and delivery routing
Implement ad matching and delivery routing Part A: Implement a data structure for an ad-matching service that supports add(campaign), remove(campaign)...
Solve Throughput, Rate Limiting, and LFU
This set of tasks evaluates algorithmic problem-solving, data structure design, and systems-oriented reasoning by testing throughput calculation, roll...
Find lexicographically smallest string and elimination order
You remember two coding questions from an online assessment. Question 1: Return the lexicographically smallest string after a prefix/suffix reverse Yo...
Determine winner in optimal-play card game
Determine winner in optimal-play card game Given a row of N cards with integer values (values may be positive, zero, or negative), two players alterna...
Implement Kac ring with O(1) color and kstep
You are implementing a Kac ring dynamical system. Model - There are N positions arranged in a circle, indexed clockwise: 0, 1, ..., N-1. - Each positi...