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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"10 years of experience but never worked at a top company. PracHub's senior-level questions helped me break into FAANG at 35. Age is just a number."
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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."
Design a constrained cache and secure string validator
This question evaluates proficiency in data structures and algorithms (constrained cache design), concurrent programming, complexity analysis, and sec...
Optimize a SQL query plan tree
This question evaluates understanding of relational algebra, query optimization techniques, and tree-based plan transformations such as predicate push...
Implement an LRU Cache
This question evaluates a candidate's competency in designing efficient cache mechanisms and managing time and space complexity for operations require...
Coordinate workers across two exclusive targets
This question evaluates proficiency in concurrent programming and synchronization, focusing on safe resource coordination, mutual exclusion, utilizati...
Merge K timestamped lists with timestamp coalescing
This question evaluates algorithmic skills in merging multiple sorted sequences, coalescing records by key (timestamp), merging sorted value arrays, a...
Solve four OA algorithm problems
This multi-part exercise evaluates algorithmic problem-solving across combinatorics and geometry (counting axis-aligned square subgrids), string reord...
Compute minimax grid path and network delay
This question evaluates algorithmic problem-solving in shortest-path and path-optimization contexts, specifically minimax pathfinding on a grid and si...
Count islands by requested sizes
This question evaluates a candidate's understanding of grid connectivity, identification of connected components, and the ability to aggregate compone...
Contrast TCP vs UDP; detect loss
Contrast TCP vs UDP; detect loss Contrast TCP and UDP in reliability, ordering, congestion control, connection setup, and overhead. How does TCP detec...
Compare Complete or Partial Hands
Implement a hand comparison engine for a simplified poker-like card game. Each player has a hand represented by an array of card strings. A card is en...
Solve tree distance and design file system
Solve tree distance and design file system Given a binary tree, find the maximum distance between two 'alive' nodes, where 'alive' nodes are initially...
Validate a bracket string
This question evaluates a candidate's ability to reason about paired-token matching and nested structure correctness in strings, measuring skills in p...
Partition a Target String by Source Substrings
This question evaluates understanding of string algorithms and optimal partitioning, specifically substring matching and minimizing the number of cont...
Enforce ordered execution across threads
Enforce ordered execution across threads Implement a class with three methods alpha(), beta(), and gamma() that may be called by three different threa...
Find and count target-sum subarrays
Find and count target-sum subarrays Given an integer array nums and an integer target, implement: ( 1) a function that returns true if any non-empty c...
Return the largest file size in a directory
Problem (Bash / File System) Implement a Bash function (or shell snippet) that returns the maximum file size (in bytes) under a given directory. Requi...
Check if all substrings are dictionary words
You are given a string s (letters only) and access to an English dictionary dict (a set of valid words). Return true if every contiguous substring of ...
Compress editor keystrokes into insert/delete/skip
You are implementing a simplified collaborative editor sync format. You are given: - An initial document string doc. - A list of user input operations...
Find shortest path on infinite grid
You are given an infinite 2D grid with integer coordinates. From a cell (x, y) you may move in 4 directions (North/South/East/West) by 1 cell per move...
Find the Best Meeting Point on a Grid
Find the Best Meeting Point on a Grid You are given a rectangular grid containing buildings, empty land, and obstacles: - 1 is a building. - 0 is empt...