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."
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"I recently cleared Uber interviews (strong hire in the design round) and all the questions were present in prachub."
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Compute max profit across dated stock quotes
You are given an unsorted list of price records for multiple stocks, each record as (date, symbol, price). Dates may be repeated across different symb...
Maintain pair-sum counts under replacements
You are given two integer arrays A and B and a list of operations: ( 1) Query(T): return the number of pairs (i, j) such that A[i] + B[j] = T. ( 2) Re...
Find maximum cable length by cutting
You are given N cables with integer lengths and a target K. Cut the cables into pieces of equal integer length L to produce at least K pieces; maximiz...
Design Manhattan-distance meeting point finder
Given an m×n grid with cells marked 1 for homes and 0 otherwise, choose a single meeting cell that minimizes the sum of Manhattan distances from all h...
Solve four data structure and algorithms tasks
1) Print the numbers at each level of a binary tree. Given the root, output the values level-by-level (each level on a new line or as a list of lists)...
Optimize C++ Performance with Provided Concurrency
Given a C++ codebase where threading components (threads, work queues, and synchronization primitives) are already provided, profile and optimize the ...
Compute Differences Between Catalog Trees
You are given two rooted catalog trees. Each node has a unique string key among its siblings and an associated value. Compare the two trees and return...
Implement KV store and plan type conversions
Part 1 — Versioned key-value store: Implement a data structure with set(key, value, t) and get_at(key, t) that returns the value for key whose timesta...
Compute peak concurrent drivers in 24 hours
Given delivery intervals across multiple drivers, compute the maximum number of distinct drivers simultaneously active within the last 24 hours from a...
Compute shortest paths with blocked nodes
Given a graph with nodes and edges and a designated source node s, compute the shortest distance from s to every other node. Some nodes are inaccessib...
Heapify an array into a max-heap
Given the array [6, 15, 2, 4, 3, 8, 19], apply heapify to build a max-heap using the standard in-place bottom-up method with a 0-indexed array represe...
Break a palindrome to smallest non-palindrome
Given a palindromic string s of lowercase English letters, change exactly one character to obtain a new string that is not a palindrome and is lexicog...
Compute max profit from single stock trade
Given an array prices where prices[i] is the stock price on day i, compute the maximum profit achievable with at most one transaction (one buy and one...
Implement hostname-restricted web crawler
Implement a single-threaded web crawler that, given a starting URL startUrl and an interface getUrls(url) that returns all hyperlinks on the page at u...
Find the nearest city sharing axis
You are given N cities, each with a unique name and integer coordinates (x, y). For any query city, return the nearest city that shares either the sam...
Design a single-machine LRU cache
Design an in-memory LRU cache for a single machine using a hash map and a doubly linked list to support O( 1) get and put. Explain how you handle capa...
Merge overlapping and adjacent ranges
Given an unsorted list of integer ranges represented as half-open intervals [start, end) with start < end, merge all overlapping or directly adjacent ...
Design a fixed-capacity circular queue
Design a fixed-capacity circular queue that supports enqueue(x), dequeue(), front(), rear(), isEmpty(), and isFull() operations in O( 1) time. Impleme...
Transform tree using counterpart subtree sums
Given the roots of two complete binary trees with identical structure, modify the node values of the second tree so that each node equals the sum of a...
Implement string dedup and mirror tree traversal
- String cleanup with group deletions (LeetCode-inspired): Given a string s consisting of lowercase letters, repeatedly delete any maximal contiguous ...