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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"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."
Write SQL for session analytics
This question evaluates SQL proficiency and data engineering competencies, including deduplication, joins, time-series aggregation, rolling-window cal...
Determine earliest collision among moving cars
You are given n cars moving over time. Each car has known initial state at time \(t=0\): - 1D case (straight road): - initial position \(x_i\) (mete...
Implement nested template string substitution
This question evaluates understanding of string processing, dependency resolution, recursive expansion, cycle detection, and efficiency techniques suc...
Maximize watched duration under consecutive-sum limit
You have a list of videos in a feed. Video i has duration d[i] (positive integer). A user has an “attention span” limit A. You want to select a subset...
Implement palindrome check and valid parentheses
You have 20–25 minutes per problem. Implement the following two functions and be prepared to explain your approach and time/space complexity. Problem ...
Debug and Fix Failing Unit Tests in Java
You receive a small Java project for a credit-card rewards service with three failing unit tests: calculatesTriplePointsForRestaurants, returnsUnknown...
Solve and optimize menu combo DP
Given up to N different menu items, each with a unit price, and a list of combo offers where each offer specifies quantities for some items and a tota...
Design log queries and a buffered writer
Part A — Log store with time-range queries: Implement a data structure that ingests log entries with ISO-8601 timestamps (e.g., YYYY-MM-DD HH:MM:SS) a...
Detect words formed by multiple dictionary parts
Given an array words of up to 100,000 non-empty lowercase strings (total characters ≤ 1,000, 000), return all strings that can be formed by concatenat...
Compute capacities after site closures
You are given a nested dictionary redistribution where redistribution[closed_site][dest_site] equals the additional capacity required at dest_site if ...
Compute missing letters to form original string
Implement a function that, given two strings original and typed (typed is a misspelled/partial version of original), returns the number of additional ...
Count decodings of a numeric string
Given a string s of digits representing an encoded message where '1' maps to 'A', ..., '26' maps to 'Z', and '0' cannot appear alone (it must be part ...
Solve hierarchy distance and digit-square convergence
You have two independent tasks: A) Organization hierarchy distance Given a list of (employee, manager) pairs that form a complete hierarchy (a single ...
Group words into anagram lists
Given an array of strings, group the words into lists of anagrams and return the collection of groups in any order. For example, ["abc", "cab", "edf"]...
Count palindrome substrings in a string
Given a lowercase ASCII string s, count the number of substrings that are palindromes and return the count. Implement an O(n^ 2) solution using expand...
Solve grid path and top‑k frequency
Part A — Grid Reachability with Obstacles: Given an m×n matrix of 0s and 1s where 0 indicates a passable cell and 1 indicates a blocked cell, starting...
Compute vertical order of a BST
Compute the vertical order traversal of a binary search tree. Define coordinates so the root is at column 0, row 0; the left child is (col−1, row+ 1) ...
Simulate views on an n-ary tree
Given a rooted, ordered n-ary tree (each node has a value and an ordered list of children), simulate an observer who starts at the bottom-left, moves ...
Justify choosing JavaScript for interviews
If given a choice of language, why would you choose JavaScript for front-end interview coding? Compare trade-offs versus TypeScript or Python regardin...
Detect runs and collapse a numeric grid
You are given an m x n grid of digits (0– 9). Phase 1: Find every horizontal or vertical run of length ≥ 3 consisting of the same digit. For each run,...