## Kings on a Chessboard

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emlightened
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### Kings on a Chessboard

Suppose there are two kings (W and B) on opposite corners of a chessboard:

Code: Select all

`W░▓░▓░▓░░▓░▓░▓░▓▓░▓░▓░▓░░▓░▓░▓░▓▓░▓░▓░▓░░▓░▓░▓░▓▓░▓░▓░▓░░▓░▓░▓░Y`

White goes first. The kings may only move to adjacent and diagonally adjacent squares. Once a king moves onto a square, neither player can move onto that square again. The first player that has no moves available loses.

Kings are not allowed to move into check.

Assuming optimum play, which player wins?

Edit: Added that kings are not allowed to move into check, and relabelled X and Y to White and Black, to make things clearer.
Last edited by emlightened on Sun Sep 27, 2015 5:34 pm UTC, edited 1 time in total.

jestingrabbit
Factoids are just Datas that haven't grown up yet
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### Re: Kings on a Chessboard

This actually looks like a new puzzle to me. And, if I've got the answer right, its quite neat.

Spoiler:
Y mirrors X ie X's moves can be written as compass moves (N, NE, E, SE, S, SW, W, NW), and Y translates those moves into (S, SW, W, NW, N, NE, E, SE), so the board always has 180 degree symmetry, and so whenever X can move, Y can move.

Relates back to an old favourite. http://www.forums.xkcd.com/viewtopic.php?f=3&t=155

redundant with the check rule.
ameretrifle wrote:Magic space feudalism is therefore a viable idea.

Gwydion
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### Re: Kings on a Chessboard

I agree with Jestingrabbit, but only if the kings only care about the spaces they're on. If we add the rules of chess, meaning kings can't move into check, that solution could fail- as soon as white moves into rows 4-5 in columns D-E, black can't legally follow but might have other asymmetric moves. I still think white can force a win but can't prove it yet...

emlightened
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### Re: Kings on a Chessboard

Sorry, I did mean to add that the kings can't move into check. Editing now.

Not exactly sure how to approach this. Do you want to try to stay one away from the edge of the board, to stop the opponent from going that way, whilst still being able to go down it yourself?

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measure
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### Re: Kings on a Chessboard

This seems remarkably similar to Tron, except with alternating discrete movement.

Yrgos
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Joined: Fri Nov 06, 2015 10:33 pm UTC

### Re: Kings on a Chessboard

Is an exhaustive search of the game tree possible? Max number of moves is 62 and the will only be a few times where you have 7 spaces to go to, most times quite a few less.

Perhaps an intelligent exhaustive search where you start with landgrabbing and play "intelligently"

taemyr
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Joined: Fri Jan 26, 2007 12:14 pm UTC

### Re: Kings on a Chessboard

Yrgos wrote:Is an exhaustive search of the game tree possible? Max number of moves is 62 and the will only be a few times where you have 7 spaces to go to, most times quite a few less.

Perhaps an intelligent exhaustive search where you start with landgrabbing and play "intelligently"

Exhaustive search is not feasible.

7^62=2.48*10^52

However as you not there will be a lot of cases where one have less than 7 moves available. This helps, but not enough. If we assume a geometric mean of 4 for the number of available moves we get 4^62=2.13*10^37 different game lines.