Coding & Algorithms Interview Questions
Practice 3,469 real Coding & Algorithms interview questions for 2026. Covers companies like Meta, Amazon, Google, Uber, and Microsoft. Real questions from actual interviews with detailed solutions — ideal for focused interview preparation. Coding & Algorithms interview questions are the single most common technical gate for software engineering roles and are used to evaluate problem framing, algorithm selection, complexity trade-offs, correctness, edge-case reasoning, and clear communication under time pressure. Expect this category to appear in early technical screens and repeatedly across onsite loops at companies that weight it heavily (notably Meta, Google, and Amazon). Interviews will test arrays and strings, trees and graphs, dynamic programming, hashing and two‑pointer techniques, and the candidate’s ability to test and optimize code in a shared editor. Prepare with timed mock interviews, practice in the same editor you’ll use live, and build a progressive schedule that moves from fundamentals to medium/hard problems; typical candidates invest several weeks to a few months of focused practice depending on seniority and target company.
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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."
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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...
Find duplicates in a list efficiently
Given a Python list that can contain integers (possibly negative) and may be very large, write code and explain approaches to find all values that app...
Compute optimal matrix-chain multiplication order
Matrix Chain Multiplication: Optimal Parenthesization and Analysis You are given five matrices to multiply: A1 (10×30), A2 (30×5), A3 (5×60), A4 (60×2...
Reverse a list in-place
Coding Task: Reverse a List In-Place (Python) Context You're implementing a utility function during a technical screen. The function must reverse a Py...
Design structure for first unique login user
You are given an online stream of user login events. Each event is a user ID (e.g., an integer or string) indicating that this user has just logged in...
Maximize min+max of contiguous subarray
You are given an array of n positive integers nums. Find a contiguous subarray that contains at least two elements and maximizes the value: > (minimum...
Match a string with wildcard pattern recursively
This question evaluates proficiency in string pattern matching, recursive problem decomposition, and algorithmic optimization including handling wildc...
Count Special Subarrays by Modular Frequency
You are given an integer array nums, and two integers modulo and target, where 0 <= target < modulo. Call an index i special if nums[i] % modulo == ta...
Find missing value in sorted consecutive array
Given a sorted array nums of distinct integers. The numbers are supposed to form a consecutive sequence starting from some unknown integer start: - If...
Implement KV Store and Token Bucket
This question evaluates a candidate's skills in implementing core data structures and concurrent algorithms, specifically in-memory key-value store de...
Find minimum operations to make array sorted
Problem You are given an integer array a of length n. Define one operation as follows: 1. Remove the first element x = a[0]. 2. Append x to the end of...
Compute maximum path sum in a binary tree
Question You are given the root of a binary tree where each node contains an integer value (which may be positive, zero, or negative). Return the maxi...
Minimize operations to reduce price difference
You are managing an inventory of products and want to adjust their prices. There are n products. The price of the i-th product is given by an integer ...
Maximize memory capacity with primary-backup servers
You are helping to optimize the capacity of a cloud system. There are n servers, where n is always even. The memory capacity of the i-th server is giv...
Find longest substring without repeating characters
Problem Given a string s, find the length of the longest contiguous substring that contains no repeated characters. Input - A string s (may contain le...
Find two numbers that sum to target
Problem You are given an integer array nums (length n) and an integer target. Return the indices (i, j) such that: - i != j - nums[i] + nums[j] == tar...
Implement a Log Rate Limiter
This question evaluates a candidate's ability to design and implement time-based rate limiting and stateful event tracking using appropriate data stru...
Implement k-th largest in a number stream
You are designing a small library to monitor statistics over a stream of integers. Implement a data structure that, given an integer k and an initial ...
Token Bucket Rate Limiter with Lazy Refill Backed by a Cache
Token Bucket Rate Limiter with Lazy Refill Backed by a Cache You are building the enforcement layer of a rate limiter. Every user has a token bucket s...
Implement dynamic batching for token decoding
You are given a black-box “simulated language model” interface that can advance many sequences in a batch. Model interface - Tokens are integers. - mo...