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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"Discovered PracHub 10 days before my interview. By day 5, I stopped being nervous. By interview day, I was actually excited to show what I knew."
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Minimize maximum height along a grid path
You are given an m x n grid heights of distinct integers representing terrain heights. You start at the top-left cell (0,0) and want to reach the bott...
Compute minimal transfers to settle group expenses
Problem A group of friends go on a trip and share expenses. Each expense is recorded as an object: - payer (string): who paid the full amount - amount...
Implement follow graph with snapshots
Problem You are building an in-memory social network relationship store that supports time-travel queries. Users are identified by integers. A directe...
Extend a Maze Solver
You are given an existing Python maze solver and a suite of unit tests. The maze is a 2D grid that uses # for walls, . for open cells, S for the start...
Sample a string by real-valued scores
You are given: - A list of strings texts (e.g., user comments), length n. - A list of floating-point scores scores of length n, where each score can b...
Debug a PyTorch U-Net shape mismatch
You are given a PyTorch implementation of a U-Net-like segmentation model that should follow the original U-Net style with valid convolutions (no padd...
Validate whether a given sequence is a Hamiltonian path
You are given strArr, an array of three strings describing an undirected graph and a proposed vertex visit order: 1. strArr[0]: a comma-separated list...
Compute minimum time with task cooldowns
You are given a multiset of task types represented by uppercase letters (e.g., A, A, A, B, B, C). Each task takes exactly 1 time unit to execute. Runn...
Find Earliest Full Connectivity Timestamp
You are given: - A list of all user IDs in a ride-sharing system. - A chronological text log of ride-sharing events. Each relevant event contains a ti...
Solve Three Algorithm Variants
You are given three independent coding problems. For each one, describe and implement an efficient solution. 1. Generate queue arrangements - You a...
Find the Next Larger Palindrome
Given a positive integer n, return the smallest integer strictly greater than n whose decimal representation is a palindrome. A palindrome reads the s...
Implement a DAG task graph
Implement a class TaskGraph to represent a directed acyclic graph of tasks. Support these operations: 1. add_task(task_id: str) -> None: Add a task if...
Determine whether points form squares
Problem: Square detection and counting from point coordinates You are given points on a 2D plane with integer coordinates. Part A — Validate a single ...
Reverse nodes in even-length linked-list groups
Problem Given the head of a singly linked list, you will traverse the list in contiguous groups of increasing size: the 1st group has size 1, the 2nd ...
Assign Pins to Shortest Columns
You are given a list of pins, where each pin has a height, and a fixed number of columns in a masonry-style layout. Process the pins in their original...
Count connected components in a binary grid
You are given an m x n grid of characters '0' and '1': - '1' represents land - '0' represents water Two land cells are connected if they share an edge...
Evaluate an arithmetic expression
Given a valid string expression containing non-negative integers, spaces, and the operators +, -, *, and /, return the computed result. Requirements: ...
Solve three easy algorithm problems
You are given three independent algorithmic tasks. For each one, explain your approach (no need to run code). 1) Merge two sorted lists (integers inst...
Implement merge sort and largest 1-rectangle
The coding round included two algorithm questions: 1. Implement merge sort for an array of integers. Return the sorted array and explain its time and ...
Minimize travel cost with two cities
You are scheduling candidates to attend an onsite interview. Each candidate i can fly to New York for cost c1[i] or to San Francisco for cost c2[i]. C...