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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Sample a string by real-valued scores
This question evaluates probabilistic sampling, numerical stability, and algorithmic implementation skills for weighted selection under floating-point...
Simulate meeting-room bookings and return busiest room
This question evaluates a candidate's competence in scheduling and resource-allocation algorithms, focusing on simulation of interval-based bookings, ...
Write SQL using joins and window functions
SQL Coding: Rank within Groups with Joins You are given two tables: accounts - account_id (string) - customer_id (string) - segment (string) — e.g., "...
Implement a crypto order management system
You are building an in-memory crypto order management system. You must parse commands from standard input and print outputs for query commands. Order ...
Implement a custom list with iterator and map
This question evaluates proficiency in data structures and generic collection implementation, specifically list operations, iterator semantics, and hi...
Answer common graph, grid, and array tasks
This set of problems evaluates algorithmic skills across arrays, graph theory, and grid/matrix traversal—covering sliding-window and contiguous-segmen...
Find accessible devices via nested memberships
Problem You are given an access model with nested groups: - A group can contain users and also contain other groups (subgroups). - A user can own or b...
Find Windows Containing a Target
This question evaluates array traversal and interval-containment reasoning, including handling inclusive endpoints, overlapping intervals, and preserv...
Implement Minesweeper and Word Search
This multi-part prompt evaluates grid-based algorithmic skills, including randomized board construction with neighbor counting, straight-line pattern ...
Count completed car journeys from sensor logs
You are given a time-ordered list of highway sensor logs. Each log entry contains: - timestamp (integer; strictly increasing) - sensor_type (one of "E...
Design Tic-Tac-Toe and QPS data structures
You are given two independent coding problems that focus on data structure and API design. --- Problem 1: Generalized Tic-Tac-Toe Game with Simple AI ...
Implement String Encryption and Decryption
This question evaluates understanding of string encoding and mapping, including handling non-bijective character-to-code relationships and performing ...
Explain differences between Python list and tuple
In Python, what are the key differences between a list and a tuple? Cover: - Mutability and implications - Performance and memory considerations (high...
Find target-heavy sliding windows
This question evaluates array manipulation, counting and efficient algorithm design—focusing on the sliding-window technique for detecting and quantif...
Sort a Large Array Using Multiple Threads
Sort a Large Array Using Multiple Threads You are given a large array of integers nums and a thread count k. Sort the array in ascending order using m...
Find gaps between intervals
You are given a list of integer intervals intervals, where each interval is represented as [start, end] (inclusive), and start <= end. Two intervals m...
Find k closest values in a BST
Find k closest values in a BST Given a binary search tree with n nodes and a real target t, return k node values whose distances to t are smallest. Im...
Validate a Binary Search Tree
Validate a Binary Search Tree Problem Given a binary tree, return whether it is a valid binary search tree. For every node, every value in its left su...
Implement a Constant-Time Random Pool
This question evaluates a candidate's ability to design and implement an efficient data structure supporting average O(1) add, remove, and uniform ran...
Implement Cache Eviction And Seat Assignment
This question evaluates understanding of data structure design and algorithmic reasoning, covering cache eviction policies (least-recently-used) and s...