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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Minimum Character Changes to Make Every k-Length Block a Palindrome
Minimum Character Changes to Make Every k-Length Block a Palindrome You are given a password string and an integer k. The length of password is guaran...
Explain arrays and memory layout
What is an array? How is an array represented in memory (contiguous layout, element size and alignment, indexing arithmetic). Analyze time complexitie...
Compute transfers to balance account debts
Problem: Balance accounts by generating transfers You are given a dictionary/map balances from accountId -> netBalance. - A positive balance means the...
Maximize pay by flipping k rest days
Given integers BasePay and Bonus, a binary string schedule of length n where '1' means work and '0' means rest, and an integer k, you may change up to...
Convert stack samples to execution trace
You are given sampling-profiler output: a list of Sample objects ordered by timestamp ascending. Each Sample has (t: float, stack: list[str]) where st...
Simulate turn-based monster team battle
Design an object-oriented model and implement the core battle logic for a turn-based fight between two teams of monsters. The system should simulate t...
Find flush and straight groups in cards
You are given an array of strings cards, where each string represents a distinct playing card. Each card string has the format <rank><suit>: - rank is...
Place Non-Attacking Queens
Given an integer n, return all valid configurations for placing n queens on an n x n chessboard so that no two queens attack each other. A queen attac...
Solve BST and Grid Query Problems
This question evaluates understanding of binary search tree order-statistics and grid reachability under threshold constraints, testing competencies i...
Track Expiring GPU Credits
This question evaluates event-replay and time-window accounting skills, including temporal data structures, priority-based consumption, out-of-order e...
Simulate Turn-Based Monster Battles
This question evaluates the ability to implement a turn-based battle simulation with correct state management, turn semantics, knockout handling, dama...
Design a max-stack with efficient operations
Design a max-stack with efficient operations Design a stack that supports push (x), pop(), top(), peekMax(), and popMax(). The popMax operation must r...
Solve five hard algorithm problems
This set of problems evaluates algorithm design and problem-solving skills across array manipulation, range-update techniques, load-balancing and part...
Implement a persistent sharded key-value store
Problem Implement a simple key–value store that persists data on disk. You must store the data in fixed-size shards, where each shard is saved in one ...
Compute max team size with a core interval
You are given n employees’ working-time intervals, where employee i works during the inclusive interval [startTime[i], endTime[i]]. You want to form a...
Implement Distributed Matrix Multiplication
This question evaluates distributed systems and parallel algorithm skills, specifically distributed matrix multiplication, data partitioning (row- and...
Add One to Digit Array
This question evaluates proficiency in array manipulation and elementary arithmetic on digit sequences, specifically carrying operations and edge-case...
Implement Datacenter Router Commands
This question evaluates proficiency in stateful command processing, input validation, geospatial computation (Haversine distance), deterministic sorti...
Merge two N-ary trees by key rules
You are given two N-ary trees A and B. Each node has: - key (string): unique among siblings (i.e., within a node’s children list, no two children shar...
Return a valid course completion order
You are given an integer n representing n courses labeled 0..n-1 and a list of prerequisite pairs prerequisites, where each pair [a, b] means you must...