Design minesweeper
PremiumMachine codingMedium
- Flood fill
- BFS
- Grid neighbours
Quick answer
This machine coding interview question asks you to design minesweeper. Aim for a design that meets its requirements at the stated scale, then explain its main components, data flow and trade-offs. Interviewers want to see how you scope the problem, size it and defend each choice.
The problem
Build Minesweeper as a game engine: a hidden grid of mines where each revealed cell shows how many of its eight neighbours are mines, and revealing a zero opens the empty area around it. The hard parts are a safe first click, flood fill on a large board and exact win and loss rules.
What must the system do?
- Create: new Game(rows, cols, mines, rng) with presets Beginner 9 × 9 / 10 mines, Intermediate 16 × 16 / 40 and Expert 16 × 30 / 99. Tests may load a fixed board instead.
- Safe first click: Mines are placed on the first reveal, never on that cell or its neighbours, so the first click always opens an area.
How well must it do it?
- No stack overflow: Flood fill must work on a 1,000 × 1,000 board with few mines, using an explicit queue or stack.
- Fast win check: Keep a count of revealed safe cells, so checking for a win is O(1).
What scale should you design for?
Use these numbers in your estimates.
The scale numbers unlock with this questionUnlock
Key concepts
- Flood fill
- BFS
- Grid neighbours
- First click safety
- Game state
- Seeded random
How you’ll practise
- Requirements
- Entities and interfaces
- Core implementation
- Edge cases and tests
- Extensions
- Wrap-up
Lala, personalized to you, gives a hint when you ask and reviews your design when you are ready.
What do interviewers look for?
In any machine coding design round.
- Clarifies the requirements before drawing anything
- Uses a few numbers that actually change the design
- Draws a clear path from the client to storage
- Picks storage and caching with reasons, not by habit
- Explains what breaks first under load and how to fix it
- States trade-offs openly instead of claiming a perfect design
Questions people ask about this interview question
- Which design type is this question?
- It is a machine coding question. You design minesweeper and explain your choices the way you would in an interview.
- Is this question asked at entry level?
- It is marked Medium. Entry-level engineers can practise it, but it expects you to reason about requirements and trade-offs, not only list components.
- What should I cover first?
- Start with the requirements: what the system must do, how well it must do it and which numbers change the design. Agree on scope with the interviewer before you design anything.
- Can I practise it for free?
- It is a premium question. Sign up and unlock it once for 10 credits; it then stays unlocked. When you finish, Lala, your personalized AI mentor, can review your design for 30 credits.
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Updated · Written by the SevyDevy team