Coding & Algorithms Interview Questions
Practice 2,960 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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Compare Complete or Partial Hands
Implement a hand comparison engine for a simplified poker-like card game. Each player has a hand represented by an array of card strings. A card is en...
Implement string-based big integer multiplication
Question Implement multiplyStrings(a, b) to multiply two non-negative integers given as decimal strings and return their product as a decimal string. ...
Solve build ordering and expression evaluation
Part A — Dependency ordering: You are given an integer n (0 ≤ n ≤ 200000) representing tasks labeled 0..n-1 and a list of prerequisite pairs [a, b] me...
Serialize and deserialize a dictionary trie
Question Design and implement serialization and deserialization for a trie (prefix tree) that stores a large dictionary of lowercase English words. Th...
Maximize grid-path expression and count sawtooth subarrays
Problem 1: Maximize a valid expression along a grid path You are given an m x n grid grid. Each cell contains either: - an operator: '+' or '-', or - ...
Assign Minimum Workers to Jobs
You are given a line-delimited text stream representing jobs. Each job record contains a start time and a duration, for example 1030 30, meaning the j...
Solve Triangle Rows and Top Frequencies
You have 1 hour to solve both coding problems. Problem 1: Build an Additive Number Triangle Given an integer numRows, return the first numRows rows of...
Implement cache and merge intervals
The interview included two coding tasks: 1. Implement a fixed-capacity key-value cache with get(key) and put(key, value). Both operations must run in ...
Generate all subsets (handle duplicates)
Problem Given an integer array nums, return all possible subsets (the power set). Part A (no duplicates) Assume all elements in nums are distinct. Ret...
Compute minimum meeting rooms on circular day
Problem You are given a list of meetings scheduled within a 24-hour day. Time is cyclic: after 23:59 the next minute is 00:00. Each meeting is represe...
Implement a banking operations system
Implement a simple banking system that manages multiple accounts with initial balances. Support operations: deposit(accountId, amount), withdraw(accou...
Compute maximum currency exchange rate
You are given a set of currencies and the direct exchange rates between some pairs of them. Each direct exchange rate tells you how many units of one ...
Simulate Threshold Grid Infection
You are given an m x n binary grid where 1 means infected and 0 means healthy, along with an integer K. The system evolves in discrete time steps. Dur...
Solve SQL and Python coding tasks
You are given a small library system with the following relational schema and several Python data-processing tasks. Answer the SQL questions and imple...
Maintain a Stream Median
Design a data structure for a stream of integers. It must support the following operations efficiently: - add_num(x): insert an integer x into the str...
Simulate Plant Infection With Controlled Burning
You are given an R by C grid of plants. Each plant is initially healthy, infected, recovered, or dead. A plant has up to four orthogonal neighbors. De...
Implement a Snowflake Query Client
Build a lightweight query client for a Snowflake-like data warehouse. Implement a QueryClient that can: 1. Connect to the warehouse using configuratio...
Implement an In-Memory Database
Implement a simple in-memory relational database that processes a sequence of tokenized commands. You are given commands: List[List[str]], where each ...
Merge two sorted linked lists
Given two singly linked lists sorted in ascending order, merge them into one singly linked list that is also sorted in ascending order. Requirements: ...
Design a 25,000-CSV ETL pipeline
You state that you built an ETL pipeline to preprocess 25,000 CSV files and load the results into a centralized database. Design the pipeline in a way...