Illegal positions where the king cannot reach its current position

miguel-ambrona / sherlock

A chess library written in Rust, oriented to creating and solving chess compositions with especial emphasis on retrograde analysis.

MIT License

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Illegal positions where the king cannot reach its current position #44

Closed hwatheod closed 4 weeks ago

hwatheod commented 1 month ago

Sherlock doesn't detect these positions as illegal: 8/8/8/8/8/P3P2P/1PPP1PP1/2k2K2 w - - 3k1b1K/4ppp1/7p/8/8/8/8/8 w - - 8/8/8/8/8/6P1/6P1/R3K2k w Q -

Issue

In all cases, one of the kings couldn't have reached its current position without moving into check. Note that the last example relies on white's king being unmoved.