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Topic: Retrograde Chess I (Read 3050 times) |
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ThudnBlunder
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Retrograde Chess I
« on: Apr 15th, 2003, 5:20pm » |
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The retrograde analysis problem I sent William seems to be inaccessible at the moment.
So, borrowing Boody's ASCII board, here it is:
WHITE:
Knight at a1
Rook at b1
King at c1
Pawns at b2, c2, and d2
BLACK:
King at a2
What was the last move played?
// 8:30 PM 3/26/2005 edited by admin to include chessboard GIF image; fixed broken image link on cover site
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| « Last Edit: Mar 26th, 2005, 8:30pm by william wu » |
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THE MEEK SHALL INHERIT THE EARTH.....................................................................er, if that's all right with the rest of you.
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Ulkesh
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Re: Retrograde Chess I
« Reply #1 on: Apr 15th, 2003, 5:52pm » |
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Well, black couldn't have moved, as he would have moved out of check by a pawn, and as the pawns haven't moved, he must have moved into check at some point, which isn't allowed.
The only possibility I see is Kxc1.
Black must have moved a knight in from b3, d3 or e2 to c1 the move before that, as there is no other way for a piece to get there. So the king moved from d1 to capture a knight on c1.
Incidentally, the knight couldn't have captured on a1 as the only piece which could have got there on black's move is a knight, and it must have come from the same position the white knight captured from (b2), which obviously isn't possible.
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| « Last Edit: Apr 15th, 2003, 6:52pm by Ulkesh » |
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mistysakura
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Re: Retrograde Chess I
« Reply #2 on: Apr 15th, 2003, 9:42pm » |
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I don't see how you can even reach this position legally. There's no way the Black king could have got there. Or should I just ignore that and go on?
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towr
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Re: Retrograde Chess I
« Reply #3 on: Apr 15th, 2003, 11:16pm » |
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The black king could have gotten there from behind the white pawn.. not even necessarily by cooperative play..
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Wikipedia, Google, Mathworld, Integer sequence DB
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BaH
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Re: Retrograde Chess I
« Reply #4 on: Dec 30th, 2005, 1:27pm » |
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if we assume that the black king has been sitting on that spot for some time, then the white king must have been the last move. if the knight had been at b3, then whites move would have been rook to a1 for checkmate. and the only 2 pieces that could have moved last were the knight and the white king.
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Skeeter
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Re: Retrograde Chess I
« Reply #5 on: Aug 21st, 2006, 8:24am » |
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it seems to me that given the perspective everyone seems to have taken on this, there is no solution given the current setup (presuming we are following normal chess rules). even if white moved most recently, black would have had to have moved out of check the previous turn, and thus would have had to move into check the turn before that, regardless of what white's two moves were.
however, there is a solution following standard rules if you simply alter your perspective a bit. actually three that i can think of.
of course its possible that i'm way off base here.
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rmsgrey
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Re: Retrograde Chess I
« Reply #6 on: Aug 21st, 2006, 10:19am » |
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on Aug 21st, 2006, 8:24am, Skeeter wrote:it seems to me that given the perspective everyone seems to have taken on this, there is no solution given the current setup (presuming we are following normal chess rules). even if white moved most recently, black would have had to have moved out of check the previous turn, and thus would have had to move into check the turn before that, regardless of what white's two moves were.
however, there is a solution following standard rules if you simply alter your perspective a bit. actually three that i can think of.
of course its possible that i'm way off base here. |
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The first reply contains a convincing answer from the traditional perspective.
Since the problem statement specifies the squares the pieces are on rather than just offering a picture of the board, the answer I suspect you intend doesn't work under my understanding of the rules of chess.
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Barukh
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Re: Retrograde Chess I
« Reply #7 on: Aug 22nd, 2006, 11:54am » |
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I think this nice problem has a perfectly valid solution from the very tranditional perspective (i.e. the bottom of the picture is White's side), and the last move is White: Kd1:Nc1.
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Skeeter
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Re: Retrograde Chess I
« Reply #8 on: Aug 22nd, 2006, 12:23pm » |
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hrm. apparently it took the 300th reading for me to comprehend that solution in the first reply you speak of.
yes, that is a perfectly reasonable solution, now that i take the time to understand.
err...i mean, i was just trying to think outside the box. 
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