Coding & Algorithms Interview Questions
Practice 3,469 real coding and algorithms interview questions reported from interviews at Meta, Amazon, Google, Uber and Microsoft. The mix follows what these loops actually ask: arrays and strings, hash maps, two pointers and sliding windows, binary search, linked lists, trees and graphs, BFS and DFS, recursion and backtracking, dynamic programming, heaps and priority queues, and the occasional design-a-data-structure round. Roughly four in five are rated medium, which is where most technical screens sit; 477 are hard and cluster in onsite loops. 3,033 of them open in a console where you can run your solution against the test cases in Python, Java, C++ or JavaScript. 2,712 come from Software Engineer interviews, with the rest from Machine Learning Engineer, Data Scientist and Data Engineer loops, and 404 were set as take-home projects rather than live sessions.
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"I've used LC, Glassdoor, and random Discords. Nothing comes close to the accuracy here. The questions are actually current — that's what got me. Felt like I had a cheat sheet during the interview."
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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."
Compute moving and weighted averages from a stream
This question evaluates a candidate's understanding of streaming algorithms, sliding-window statistics, and resource-constrained data structure design...
Assign bookings to minimum tennis courts
This question evaluates interval scheduling and resource-allocation competencies, testing algorithmic and data-structure knowledge for handling time-i...
Solve prefix, array, and string problems
This set of problems evaluates proficiency in string and array algorithm design—covering prefix search, subsequence matching, and maximal-area computa...
Find numbers with exactly two sum-of-squares forms
This question evaluates understanding of integer representations as sums of two squares and the ability to reason about counting distinct unordered re...
Build a time-based key-value store
Problem Design a data structure that stores multiple values for the same key at different timestamps, and can retrieve the most recent value as of a g...
Implement a Tic-Tac-Toe game class
Problem Implement a class that supports playing an n × n Tic-Tac-Toe game. Requirements Create a class TicTacToe(n) with: - move(row, col, player) -> ...
Optimize invites under capacity constraints
You have n donors (n up to 100,000). For each donor i you know: p_online[i] (probability of donating if emailed), a_online[i] (expected donation condi...
Minimize L2, L1, and quantile losses
Given an array X of n real numbers, derive the value θ that minimizes the sum of squared deviations Σ(xi−θ)² (mean) and the sum of absolute deviations...
Find longest uniform substring after k replacements
Given a string s (ASCII, length up to 2e5) and integer k (0 ≤ k ≤ |s|), return the length of the longest substring that can be turned into all the sam...
Maximize products bought under budget
Given N products and M customers, for each customer find the list of distinct products they can buy without exceeding their budget such that the numbe...
Implement lazy unique-merge generator for sorted streams
Write a Python generator merge_unique(a, b) that lazily merges two nondecreasing iterables a and b (potentially infinite) into a single nondecreasing ...
Compute array modes with ties and no-mode rule
Write a function that returns the mode(s) of an integer array. Requirements: if all values are unique, return an empty list (there is no mode); allow ...
Compute max island with constrained flips
Given an n×n binary grid G where 1=land and 0=water with 4-directional connectivity, return the size of the largest island achievable by flipping at m...
Solve stock, BFS path, and merge intervals
Solve three coding problems; justify complexity and corner cases. A) Best Time to Buy/Sell Stock (one transaction): Given prices[0..n-1] (integers), r...
Solve and optimize 3Sum and variants at scale
Implement a function that returns all unique triplets (i, j, k) of indices whose values sum to a target T, with strong performance and deduplication g...
Implement DFS with cycle detection and topo order
Implement DFS (recursive and iterative) with topo sort, cycle detection, and timestamps You are given a directed graph G with N nodes labeled 1..N and...
Implement streaming per-user reservoir sampling
Design and code (in Python) a streaming algorithm that ingests an unbounded event stream of tuples (user_id, event_time, event_type) and maintains, fo...
Compute and Rank by Jaccard Similarity
Implement two functions: (1) jaccard_similarity(s1, s2) that tokenizes by splitting on any non-alphanumeric character, lowercases, treats tokens as se...
Solve two-pointer, sliding-window, and string tasks
Solve the following three coding tasks: 1) Two-pointer in-place de-duplication: Given a non-decreasing integer array nums and an integer k >= 1, modif...
Implement scalable prime generator
Write a function first_n_primes(n) that returns the first n prime numbers in ascending order. Constraints: - 1 ≤ n ≤ 100,000. - Aim for O(n log log n)...