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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"Literally just signed a $600k offer. I only had 2 weeks to prep, so I focused entirely on the company-tagged lists here. If you're targeting L5+, don't overthink it."
"Coaches and bootcamp prep courses cost around $200-300 but PracHub Premium is actually less than a Netflix subscription. And it landed me a $178K offer."
"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 longest rising path in a grid
Given an m×n grid of integers, find the length of the longest path where each step moves up, down, left, or right to a strictly larger value. Return t...
Optimize flight costs and find grid path
1) Given two integer arrays D and R of equal length n, where D[i] is the cost to depart on day i and R[j] is the cost to return on day j, choose indic...
Design IP/CIDR rule matcher
Design and implement a rule matcher that returns 'accept' or 'deny' for a given IPv4 address based on a set of rules. Each rule can be either an inclu...
Design file deduplication at scale
Design an algorithm to identify duplicate files in a large directory tree. You are given an iterator over files providing (path, size) and a function ...
Find earliest common meeting slot
Question Given the calendars of N attendees, find the earliest time window of length at least d minutes during which all attendees are simultaneously ...
Implement Binary Search in C++
From scratch in C++, implement binary search over a sorted array to locate a target value. Provide a correct iterative implementation, handle not-foun...
Solve vault rate and subset-sum
1) Robber vaults rate: You are given an array vaults of positive integers where vaults[i] is the amount in the i-th vault, and an integer h (hours). I...
Design faster delay-time computation
You are given an array of integers representing task priorities. Tasks execute from right to left. For each index i, define its delay time as j - i wh...
Implement string-based big integer multiplication
Question Implement multiplyStrings(a, b) to multiply two non-negative integers given as decimal strings and return their product as a decimal string. ...
Compute currency conversions with graph algorithms
Question You are given a set of pairwise currency exchange relations such as A:B = 1:1.5 and B:C = 1:1.5, meaning 1 A = 1.5 B and 1 B = 1.5 C. Design ...
Implement cocktail shaker sort and analyze
Implement the cocktail shaker sort (bidirectional bubble sort) for an array of integers. Optimize it with early termination and shrinking bounds, and ...
Solve expression evaluator and string decoder
1) Implement an arithmetic expression evaluator that reads expressions from a text file (one expression per line) and outputs the evaluated result for...
Find shortest path using BFS
Given an m×n grid grid where grid[r][c] = 0 represents an empty cell and 1 represents a wall, a start cell (sr, sc), and a target cell (tr, tc), you m...
Design room progression with leaderboard
Design a data structure to simulate a sequence of rooms where players solve tasks and can move only to the next room once finished. Support the follow...
Determine frog reachability across stones
You are given a sorted array of distinct integers stones representing stone positions in a river, where stones[0] = 0. A frog starts on stone 0; its f...
Find top co-purchased products
You receive purchase logs where each order is represented as an integer array of product IDs bought together in a single transaction. Implement a func...
Implement a ring buffer
Implement a fixed-capacity circular buffer (ring buffer) supporting push, pop, peek, isEmpty, isFull, and size in O( 1) time using an array. Define an...
Solve parsing, counting, ranges, and window problems
Solve the following four algorithm problems: 1) Expression evaluator with + and : Given a string s containing non-negative integers, '+' and '' operat...
Compute shortest path between tree nodes
Question You are given the root of a binary tree (not necessarily a BST) whose nodes have integer values, and two target values u and v. Implement a f...
Reverse sublist between equal-value nodes
Given the head of a singly linked list and a target value v that appears at least twice, reverse the sublist starting at the first node with value v a...