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."
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Dot Product of Two Vectors (Dense, then Sparse)
This question assesses proficiency in array manipulation and algorithmic efficiency by asking for a vector dot product, first over dense arrays and th...
Inventory Allocation by Bid Priority
This question assesses simulation and priority-queue design skills, requiring careful implementation of tiered, round-robin resource allocation under ...
Optimal Commute: Nearest Transit Distance in a City Grid
This question evaluates a candidate's ability to apply multi-source breadth-first search to a grid-based shortest-path problem. It tests graph travers...
Most Active Users in a Live Communication Stream
This question tests practical application of hash-based data structures and stream processing to track and rank user activity with deduplication logic...
Print the File System State
This question evaluates a candidate's ability to serialize and format in-memory data structures for deterministic textual output, focusing on represen...
Validate Adding an Edge to a Directed Acyclic Graph
Determine whether a proposed directed edge is new and can be added to an existing DAG without creating a cycle. Reject self-loops and duplicates, then...
Calculate Trapped Rain Water
Calculate how much rain water is trapped between nonnegative unit-width bars without mutating the input. A two-pointer scan tracks the highest boundar...
Reconstruct the Alphabet Order of an Alien Language
This question tests graph construction and topological sorting, core algorithmic skills for reasoning about partial orderings derived from constraints...
Implement A Contiguous Memory Allocator With Free-Block Coalescing
Review a contiguous memory allocator coding prompt with malloc, free, first-fit allocation, block coalescing, and a best-fit follow-up. The interview ...
Merge Overlapping Intervals
This question tests practical array manipulation and sorting skills by requiring candidates to consolidate overlapping numeric intervals into a minima...
Can All Courses Be Completed?
This question tests graph traversal and cycle detection skills, specifically the ability to model dependency relationships as a directed graph. It eva...
Shift Non-Zero Elements Left In Place
This question tests a candidate's ability to perform in-place array manipulation while preserving element order, evaluating practical understanding of...
Check Meeting Attendance With Breaks
This question evaluates proficiency with interval scheduling, time-format conversion, and constraint checking for sequential appointments, measuring a...
Find the Maximum Number of Concurrent Processes
Practice a Amazon coding interview problem focused on find the maximum number of concurrent processes. The prompt emphasizes edge cases, clean impleme...
Evaluate an Arithmetic Expression in Postfix Notation
Practice a Amazon coding interview problem focused on evaluate an arithmetic expression in postfix notation. The prompt emphasizes edge cases, clean i...
Find the Closest Version by Date
Practice a Amazon coding interview problem focused on find the closest version by date. The prompt emphasizes edge cases, clean implementation, and ve...
Choose the Best Travel Mode
Solve a grid-based pathfinding problem where a traveler must choose the transportation mode with the lowest travel time and cost tie-breakers. The que...
Hierarchical Access Control for an Advertising Platform
This question tests practical application of graph traversal and access control system design using a directed acyclic group hierarchy. It evaluates a...
Rearrange Tasks With Cooldown
This question evaluates task-scheduling and constraint-handling skills, testing algorithmic reasoning about arranging repeated jobs with cooldown cons...
Calculate Bowling Game Score
This question evaluates a candidate's ability to implement rule-based scoring logic, array processing, and stateful iteration to correctly aggregate f...