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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"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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Determine Whether P's Position Is Unique
You are given an R x C rectangular grid and a set of named entities. Each entity must be placed in exactly one distinct cell. You are also given a col...
Implement local maxima, bagging, and k-means
Solve the following programming tasks. 1) Find all “local maxima” in a streaming temperature array You are cleaning sensor data for temperature-fluctu...
Implement Connect Four Winner Detection
Implement a Connect Four-style game engine. The board has 6 rows and 7 columns. Two players alternate turns. On each turn, the current player chooses ...
Implement an LRU Cache
Design and implement a fixed-capacity key-value cache that evicts the least recently used item when it becomes full. Support the following operations:...
Find a Bounded Subarray and Largest Square
Implement the following two independent coding tasks. Task A: Longest bounded-range subarray Given an integer array nums and an integer limit, return ...
Implement rotated array binary search with duplicates
Given an integer array nums that is a non-decreasing array rotated an unknown number of times. Duplicates may exist. Implement a function that returns...
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 ...
Implement Longest-Match Text Replacement
You are given a text string and a dictionary of replacement entries. Each dictionary entry has the form token:id, where token is a string pattern and ...
Evaluate Symbol Expressions
You are given a map from symbol names to arithmetic expressions. Each expression may contain integer constants, other symbol names, parentheses, and t...
Compute Nearest Destination Distances
You are given an m x n grid representing a city map. Each cell contains one of the following characters: - D: a destination - X: an obstacle - .: an o...
Implement a Formula Spreadsheet
Design and implement a small in-memory spreadsheet. The spreadsheet must support cell labels such as A1 and B10, where a label consists of uppercase l...
Maximize Boundary-Difference Subarray Sum
Given an integer array nums and an integer k, find the maximum possible sum of a non-empty contiguous subarray whose first and last elements differ by...
Count Trips From Vehicle Logs
You are given a text log of vehicle events on a road system. Each log record contains: - license_plate: a string identifying a vehicle - event_type: o...
Implement IPv4 iterators and CIDR expansion
Problem: IPv4 Iterators and CIDR Expansion You are implementing utilities to iterate over IPv4 addresses. An IPv4 address is in dotted-decimal form: A...
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...
Solve expression evaluator and string decoder
1) Implement an arithmetic expression evaluator that reads expressions from a text file (one expression per line) and outputs the evaluated result for...
Design an in-memory banking service
Design an in-memory banking service supporting timestamped operations and edge-case semantics. Implement: ( 1) create_account(id, t): Create a new acc...
Implement compile-time function type verification
Implement a C++20 compile-time utility to verify whether a callable matches a target function type. Requirements: create a primary template is_callabl...
Find Shortest Queue with Few Calls
You are given a list of queues of integers. For each queue, the only available operations are isEmpty() and poll(), where poll() removes and returns t...
Implement Interval Insert and Dedup
This interview round contained two coding problems: 1. Insert and merge intervals. You are given a list of non-overlapping intervals sorted by start t...