# Chessboard Question - HELP

1. Apr 3, 2004

### SeanP

Chessboard Question - HELP!!!!

A chessboard is square of rectangular. Adjacent squares=squares with common side. A piece is put in each square of board, then they're picked up and put back down again in a way that the adjacent pieces are still adjacent.

If both pieces in the lefthand corner are kept in place and not picked up when the rest are rearranged (but still adjacent to each other as before), then is it possible for any piece to be in different positions the second time?

Would the answer to the above change if only one of the lfthand corner prices is kept fixed? Can this be generalised to any other piece remaining fixed on the board?

Can anyone help?

2. Apr 3, 2004

### Hurkyl

Staff Emeritus
One thing I do on many problems is try simpler cases. What about a 2x2 chessboard? Or maybe a 3x3 chessboard? Try generating all possible rearrangements (that preserve adjacency) in these...

3. Apr 3, 2004

### matt grime

I'm not exactly sure I understand the question. Must all but the two opposite corner pieces be moved? Basically it looks, from experience, as though you're attempting to pair up adjacent squares, ie by covering the two pieces you swap with a domino. In this case you're doing the famous 'can you cover a chess board with dominoes question'. Hint if two squares are adjacent and one's white, what must the other one be?

4. Apr 5, 2004

### SeanP

I dont understand your reference to swapping with a domino.
The other one must be black.

5. Apr 5, 2004

### matt grime

I am saying if you swap two adjacent pieces, cover their squares with a domino. But I'm not sure I understand the instructions you originally gave. Suppose we've got this set up, and I swap the piece on one square with one next to it. Am I allowed in a subsequent swap to move either of those pieces again, or have they had their move and that's that, you move on and swap another pair, if any.

If, once you've swapped over two pieces that's their move done and they can take no further part in the operation (which I think must be the case or the questions easy to answer) then when you swap a pair of pieces, one's on a white square the other is ona black square, can you see how that might help? I'm not sure that is answering your question though, now. So forget it. In fact I'm certain it doesn't - the penny has dropped and I now see what you're asking, and this isn't the answer (at least it wasn't intended to be, if it does solve it it's a fluke).

Last edited: Apr 5, 2004