Design a chess game

Hard45 minFree, no account

Piece movement is the easy half. Check, castling and en passant are the design.

The question

Design the classes for a two-player chess game: board, pieces, moves, turns, and end conditions.

Handle castling, en passant, promotion, check and checkmate.

Functional

Validate and apply a move; reject illegal ones with a reason.
Detect check, checkmate and stalemate.
Castling, en passant, promotion, the fifty-move rule and threefold repetition.
Undo, and move history in algebraic notation.

Non-functional

Adding a new piece type must not require editing the board.
Rule checks must be fast enough for a move to validate instantly.

45:00Commit to an answer before you open the solution. Reading it first teaches you to recognise good answers, which is not the skill being tested.

Stuck?

0 of 3 hints taken

The worked solution

written by a person · not a grade

Score yourself

0 of 5 marked

Separated pseudo-legal movement from legality, with the filter written once30
Derived the full game state including castling rights and en passant20
Handled all three special moves correctly, promotion as an input20
Defined checkmate and stalemate precisely from the same computation15
Covered draws: fifty-move, repetition on full state, insufficient material15

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