That is my very favorite retrograde problem. And I’m pretty sure there’s only one solution. It’s the cover of Smullyan’s Chess Mysteries of the Arabian Knights: https://images-na.ssl-images-amazon.com/images/I/91B-xKpMIFL.jpg ”The White king, Haroun al Rashid, has made himself invisible. Where is he?” (Incidentally Smullyan autographed my copy “I wish you the best, but I refuse to sign this book! Raymond Smullyan”.) Bob
On May 2, 2017, at 12:37 PM, Dan Asimov <dasimov@earthlink.net> wrote:
Cute!
(I detect two solutions; another piece could be added to prevent a second option.)
I'm still very fond of a retrograde chess problem from a Martin Gardner column, attributed to Raymond Smullyan:
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. r . b . . . .
B . . . . . . .
. . . . . . . .
. . . . . . . .
. . . k . . . .
After a legal move has been completed in a legal chess game, the white king was accidentally knocked off the board.
Puzzle: Where was the white king?
(No fair if you've already seen this.)
—Dan
From: Bill Gosper <billgosper@gmail.com>
r3k3/p1p5/Q3K3/8/8/8/8/8 w --rwg
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