Design
Tic-Tac-Toe
Design a Tic-Tac-Toe game supporting human vs human, human vs AI, and board of configurable size.
01 - Why interviewers ask this
It's often the very first LLD question asked, specifically to see whether you can identify a win-condition check as its own concern rather than a wall of nested loops.
02 - Where this system exists in the real world
You interact with this design every day.
Simple two-player board games (mobile/web)
Game engine tutorials for win-condition checking
AI/minimax algorithm teaching examples
03 - What you'll master
Solve this once. Know it forever.
Model a grid and player turns cleanly
Isolate win-condition checking as its own logic
Practice extending a design (e.g. to N x N boards)
04 - What you'll design
6 functional · 2 non-functional requirements.
Support N×N board (not just 3×3)
5 more requirements inside
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05 - Companies that ask this
You may face this exact question in your next interview.
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