Coding & Algorithms Interview Questions
Practice 3,013 real Coding & Algorithms interview questions for 2026. Coding & Algorithms interview questions for top tech firms like Meta, Amazon, Google, Uber, and TikTok — real questions from actual interviews with detailed solutions — to power your interview preparation. This collection is sharply focused on algorithmic patterns (arrays, strings, sliding windows, trees/graphs, dynamic programming, greedy, two-pointers, and hashing), clean, review-ready code, and the explanation skills that distinguish hires. In 2026 expect familiar medium-to-hard problems plus newer twists: AI-enabled or multi-file coding rounds at some companies, more emphasis on explainability and edge-case reasoning, and occasional real-world performance constraints (streaming, concurrency, memory limits). Interviewers evaluate problem framing, algorithm choice, complexity trade-offs, test-case thinking, and communication under time pressure. Best prep mixes pattern-based practice, timed mock interviews, code-review style polishing, and rehearsed explanations of complexity and tradeoffs. Focus your last-mile prep on writing correct, readable code quickly and on explaining why your solution is robust and efficient for production scenarios.
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Determine If One Binary Tree Is a Substructure of Another
Given two binary trees A and B, determine whether B is a substructure of A. B is a substructure of A if there exists some node in A such that the subt...
Minimum Bills and Coins to Make Change
You are building the change-dispensing logic for a self-checkout cash register. Given a purchase change amount (in dollars, e.g. 6.35), compute the mi...
Minimum Drone Delivery Time on a Ring of Hubs
A fleet operator runs a single delivery drone over a set of m hubs arranged in a circle (a ring). The hubs are numbered 1 through m in clockwise order...
Implement Journey Counter and Speeder Detector
You are given a highway toll log parser with two classes: LogEntry and LogFile. Each log line has the format: timestamp license_plate location booth_t...
Implement Integer Square Root
Given a non-negative integer x, implement sqrt(x) and return the integer part of its square root, i.e., floor(sqrt(x)). Requirements: - Do not use a b...
Validate transactions with risk rules and reporting
You are building a small fraud-screening validator that reads transactions from a CSV file and outputs a human-readable report. Input 1) Transactions ...
Implement string formatting and request tracking tasks
You are given several small coding tasks. Implement each as described. Task A — Convert snake_case to camelCase Write a function that converts an iden...
Find Shortest Grid Path
You are given an m x n grid where 0 represents an open cell and 1 represents a blocked cell. You are also given a start cell (sr, sc) and a target cel...
Implement Employee Validation and Snake
This interview covered two coding tasks: 1. Employee validation - Implement a function that validates a collection of employees against a set of bu...
Implement a Sparse Matrix Class
Implement a SparseMatrix class for matrices that contain mostly zero values. Your class should support the following operations: 1. Construction and s...
Implement core puzzle/array/grid routines
You may be asked to solve one or more of the following coding exercises (write clean, testable code; discuss time/space complexity): 1) Jigsaw assembl...
Simulate Monster Team Battles
Design and implement a battle simulator. Data model: - Team: a team name and an ordered list of monsters. - Monster: a monster name, a type, current h...
Maximize Boxes Stored Through One Entrance
You are given two integer arrays: - boxes[i]: the height of the i-th box. - rooms[j]: the height limit of the j-th room in a linear warehouse. The war...
Implement a Byte Pair Encoding (BPE) Tokenizer
Implement a Byte Pair Encoding (BPE) Tokenizer Byte Pair Encoding (BPE) is a tokenization algorithm widely used to build the vocabularies of modern la...
Implement buffered file writer with concurrency support
You are given a simple file writer class that writes data directly to disk: `cpp class FileWriter { public: // Append data to the file on disk imm...
Traverse an Org Chart by Level
You are given an organization's reporting structure as a flat list of employee-manager relationships. Exactly one employee is the root (the CEO) and h...
Validate password and list rule violations
Problem You are given a password string p. Validate it against a set of rules and return all rules that the password violates. Rules 1. Length must be...
Validate a Parent-Child Forest
You are given a list of directed edges, where each edge is represented as (parent, child). The edges describe parent-child relationships among nodes i...
Find Common Prefix Across Strings
Given an array of strings, return the longest string prefix that is shared by every string in the array. A prefix must start at index 0 of each string...
Implement a Resizable Deque
Implement a double-ended queue (deque) data structure backed by a circular array. Your deque should support insertion and removal from both ends and s...