Coding & Algorithms Interview Questions
Practice 2,970 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."
"I recently cleared Uber interviews (strong hire in the design round) and all the questions were present in prachub."
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Develop Auto-Complete System for Dish Suggestions
Scenario Search-as-you-type needs dish suggestions with popularity scores. Question Build an auto-complete system using the given (string, score) tupl...
Calculate 7-Day Rolling Average for Energy Consumption
Scenario Hiring manager wants a quick coding exercise to verify programming fluency. Question Write a Python function that takes a list of daily energ...
Solve Python Challenges: Reverse String, Palindrome, Fibonacci, Unique List
Scenario Live coding round – four quick Python exercises Question Implement a function that reverses a string in-place. Write code that returns True i...
Design Data Structure for Sparse Matrices Operations
Scenario Analytics engine stores extremely sparse numeric matrices. Question Design a data structure to store two sparse matrices and implement print(...
Maximize Non-Overlapping Task Scheduling Efficiency
Scenario Job scheduler on a single machine wants to maximise throughput. Question Given tasks with [start, end) times, return the maximum number of no...
Explain Python Virtual Environment Setup and Function Analysis
Scenario Technical screen where candidate and interviewer jointly walk through Python code snippets used in a data-science repository. Question Show h...
Find max consecutive elements with sum below target
You are given: - An integer array nums of length n, sorted in non-decreasing order. - An integer index such that 0 ≤ index < n. - An integer target. S...
Rotate a Matrix In Place
Given an n x n matrix of integers, rotate the matrix 90 degrees clockwise. Implement the function in Python. You may use a straightforward approach wi...
Generate outputs for images and pipelines
You are given m input images and n processing pipelines. - Each pipeline is an ordered list of k operations (e.g., resize, rotate, crop, blur, color t...
Find the Slowest Function from Profiler Events
You are given a time-ordered profiler event log for a single-threaded program. Each event is one of: - START functionName timestamp: execution enters ...
Determine if chasing points will meet
You are given N points in 2D, indexed 0..N-1, forming a cycle. - At time t = 0, point i is at coordinates (xi, yi). - All points move simultaneously a...
Find smallest N for 5-and-21 sums
You are given two positive integers: 5 and 21. We say a positive integer x is representable if it can be written in the form \[ x = 5a + 21b \] for so...
Solve Digit-Square and Grid BFS Problems
Solve the following coding problems. Problem 1: Digit-square convergence Given a positive integer n, repeatedly replace n with the sum of the squares ...
Detect Winners in Nested Tic-Tac-Toe
Implement functions for two related board-evaluation problems. Part 1: Classic Tic-Tac-Toe Given a 3 x 3 board represented by characters 'X', 'O', and...
Find shortest substring with N unique characters
You are given a string s and an integer n. Find the shortest contiguous substring of s that contains exactly n distinct characters. If there is no suc...
Compute maximum perimeter among islands
Problem You are given an m x n binary grid grid where: - grid[r][c] = 1 represents land - grid[r][c] = 0 represents water An island is a maximal set o...
Compute moving and weighted averages from a stream
You are processing a stream of numeric events (e.g., user activity counts). You are given a fixed window size X. Part 1: Moving average over last X va...
Build referral chains and detect cycles
You are given a directed referral graph where each user may have at most one referrer. Input file 'referrals.csv' has columns: user_id (INT), referred...
Implement max profit with K transactions (DP)
Given an array prices[0..n-1] of daily stock prices and an integer k, implement a bottom-up dynamic program to compute the maximum achievable profit w...
Design robust group size limiting for calls
Design the admission-control and enforcement algorithm to limit group-call size under real-world race conditions. Constraints: multiple SFU edges in m...