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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"I honestly don't know how you guys gather so many real interview questions. It's almost scary. I walked into my Amazon loop and recognized 3 out of 4 problems from your database."
"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."
"The search is what sold me. I typed in a really niche DP problem I got asked last year and it actually came up, full breakdown and everything. These guys are clearly updating it constantly."
Solve DFS grid and keypad problems
You may be asked to solve one or more DFS/backtracking problems: 1. Grid connectivity problem: Given an m x n grid where 1 represents land and 0 repre...
Implement K-Means and Explain Convergence
Implement the K-means clustering algorithm for points in Euclidean space. Your implementation should: - take a dataset of points and a target number o...
Solve four algorithmic library problems
Solve the following coding tasks: 1) Maximum Points from Different Categories: Given an array of items (category, points) and an integer k, choose exa...
Find nearest room; extend to two users
You are given an m×n grid where 1 is a wall (impassable), 0 is an empty cell, and 2 is a meeting room. From a starting coordinate [r, c], you may move...
Design BFS to detect forced win in Tic-Tac-Toe
You are given an n×n Tic-Tac-Toe–like board and a target k (1 ≤ k ≤ n). From the current board state and the player to move, design an algorithm to de...
Implement in-place duplicate removal
Given a non-decreasing array of integers, overwrite it in-place so that each distinct value appears exactly once while preserving the order of the uni...
Find the kth largest element
Given an unsorted array of n integers and an integer k (1 ≤ k ≤ n), return the k-th largest element without fully sorting the array. Design two method...
Produce a valid deployment order
You are given N services and a list of dependency pairs (A, B) meaning service B must be deployed before service A. Compute any valid deployment order...
Remove runs of length at least k
Given a string s and an integer k (k >= 2), repeatedly remove every maximal contiguous group of the same character whose length is at least k, deletin...
Implement crawler and file deduplication
The interview included two coding exercises: 1. Build a web crawler starting from a seed URL within a single domain. First implement a single-threaded...
Count subarrays equal to target
Given an integer array nums and an integer k, count the number of contiguous subarrays whose sum equals k. Solve it in O(n) time and O(n) space by mai...
Design a hierarchical locking tree
Design a LockingHierarchy data structure over a rooted tree of N nodes labeled 0..N-1, initialized with an integer array parent[] where parent[0] = -1...
Compute peak busy dashers with overlaps
You are given delivery logs as (dasherId, startTime, endTime) with integer times, where endTime is exclusive. A single dasher may accept multiple orde...
Implement a formatted shell script output
Write a shell script named script.sh that is invoked as: ./script.sh <username> <path_of_file>. It must print a single line formatted exactly as: <tim...
Find longest unique substring
Given a string s, find the length and one example of the longest substring of s that contains no repeated characters. If multiple answers exist, retur...
Solve three coding tasks: binary search, tree path, subarray
Solve the following coding tasks: 1) In a sorted array, every value appears exactly twice except for one value that appears once. Find the single valu...
Solve three algorithmic optimization and search problems
You are given three independent coding problems. --- Problem 1: Allocate tasks between two workers to maximize reward You have n independent tasks tha...
Design algorithms for test scheduling
You have tens of thousands of graphics test cases with inter-test dependencies and hardware/driver constraints. Model this as a graph and design algor...
Determine string segmentability with dictionary
Given a string s and a dictionary of words, determine whether s can be segmented into a sequence of dictionary words. Provide a dynamic-programming so...
Count expressions reaching a target sum
Given an array of non-negative integers nums and an integer target T, assign either a + or − sign to each number to form an expression. Count how many...