FA-82755 / Chess move legality / Member archive

K right assigned to the inner rook · case 05

With rooks on e1 and h1 and the king on c1, the K right maps to e1.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

Input: {"board", "rights"}: rights letters are K/Q (outermost own rook on the back rank on the king's h-side / a-side), file letters A-H or a-h (the own rook on that file), or "-". A right only counts if the king is on its back rank (rank 1 for white, 8 for black) and the rook exists. Return the sorted distinct list of rook squares that carry castling rights.

Why this case matters

Chess960 and X-FEN positions encode castling by rook file; a wrong mapping castles with the wrong rook.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
two rooks on h-side	`["e1"]`	`["h1"]`	Failed

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