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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Compute balances with transaction fees and rejections
This question evaluates transaction processing, ledger state management, handling of edge cases like insufficient funds and fixed fees, and efficient ...
Implement undo/redo with two stacks
This question evaluates a candidate's ability to design and implement efficient mutable state management and history tracking using data structures (s...
Count connected components in a binary grid
This question evaluates understanding of graph traversal and connected-components detection on a 2D grid, measuring the ability to model grid cells as...
Implement a rule-based rate limiter
This question evaluates a developer's ability to implement real-time rule-based rate limiting, covering rule matching, time-windowed quota enforcement...
Remove duplicates and find constrained longest subsequence
This question evaluates data structure manipulation and string-processing competencies, specifically linked-list deduplication and finding the longest...
Implement chance of a personal best
You are given a simplified model for tracking race times on an obstacle course. - A course has a fixed number of obstacles. - A run records the time s...
Compute total after discounting most expensive item
This question evaluates array manipulation and numeric computation skills—specifically identifying the maximum element, applying a percentage discount...
Implement Longest-Match Text Replacement
You are given a text string and a dictionary of replacement entries. Each dictionary entry has the form token:id, where token is a string pattern and ...
Solve remembered OA coding tasks
The online assessment reportedly had five coding questions, but only the following three were described clearly enough to reconstruct: 1. Find the top...
Count ordered fragment pairs forming a password
This question evaluates proficiency with string manipulation, handling duplicate fragments, and combinatorial reasoning about ordered index pairs that...
Simulate round-robin package assignment to servers
This question evaluates array-based simulation and control-flow skills for load distribution, including pointer management, modular wrap-around scanni...
Implement an IPv4 Iterator
This question evaluates proficiency in IPv4 address representation and arithmetic, CIDR parsing, iterator API design for forward and backward traversa...
Compute maze score using shortest path
You are given a grid-based maze game. - The maze is an R x C grid of characters: - '#' = wall (cannot pass) - '.' = empty cell - 'S' = current p...
Move zeros to front
This question evaluates array manipulation and in-place algorithm skills, specifically competency in stable element reordering, index management, and ...
Implement wildcard querySelector to extract URL
This question evaluates implementation skills for a simplified selector engine, DOM traversal and manipulation, wildcard attribute pattern matching, a...
Maximize score in 15-sum card game
This question evaluates algorithmic problem-solving in combinatorial search, state-space optimization, and memoization by asking for the maximum achie...
Implement two string utility functions
Implement the following Python functions: 1. number_of_character(string, char) - Return the number of times character char appears in string. - ...
Write SQL for session analytics
This question evaluates SQL proficiency and data engineering competencies, including deduplication, joins, time-series aggregation, rolling-window cal...
Compute shipping cost with tiered pricing
This question evaluates the ability to implement tiered billing and aggregate shipping costs across order line items, testing competencies in algorith...
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 ...