[Guest]

An evil Emperor was bored one day so he decided to play chess… human chess that is!

So he went to the dungeon and found 16 tough prisoners and 16 prison guards and told them the following:

“Tomorrow morning you prisoners will choose from a set of chess piece costumes and weapons (either the white or the black) so that you are the same color. The guards will get the other color. The prisoners will then choose any squares they desire on the large chess board in my courtyard, and then the guards will choose.”

“The rules will be like a normal chess game except the starting configuration is chosen by the players. I will play the guards and the prisoners king piece will play for them. The team that moves a piece resulting in checkmate wins and the other side is executed. The team that moves a piece resulting in stalemate is executed. “

“And because I am so gracious, any prisoners that are not dead at the end of the game will be set free. See you tomorrow… HEHE HOHO COUGH COUGH”

You and your fellow prisoners have the night to sweat out a plan. They decide you look like a nerd so they elect you to play the king in tomorrow’s game. One of the prisoners who has been there a while says he has seen the guards play many times before, and that if they are not blocked, they always arrange themselves in the same way. He sketches in the dirt the familiar starting arrangement of chess pieces with rook in the corner then knight, bishop, K, Q, etc. and a row of pawns across.

The other prisoners are looking at you doubtfully and suddenly you wish you had been more of a chess nerd!!

1.) How will you position your pieces for maximum survival?

2.) Is there a way to guarantee the survival of some prisoners? How many?

[Guest]

Interesting problem. My first thought is to put most of the pawns one step away from the other side (so in one move they can become queens). Surround your king with the other pieces (perhaps in one corner). Second thought is - there is one side that the king is weak on (king side in front of the bishop). Make it so you can move your queen to this spot on your first move and their king is immediately in checkmate and your queen is covered by another piece like a knight. However, if you place pieces like that, the king would probably change his placement. I'll have to think of some other methods.

An evil Emperor was bored one day so he decided to play chess… human chess that is!

So he went to the dungeon and found 16 tough prisoners and 16 prison guards and told them the following:

“Tomorrow morning you prisoners will choose from a set of chess piece costumes and weapons (either the white or the black) so that you are the same color. The guards will get the other color. The prisoners will then choose any squares they desire on the large chess board in my courtyard, and then the guards will choose.”

“The rules will be like a normal chess game except the starting configuration is chosen by the players. I will play the guards and the prisoners king piece will play for them. The team that moves a piece resulting in checkmate wins and the other side is executed. The team that moves a piece resulting in stalemate is executed. “

“And because I am so gracious, any prisoners that are not dead at the end of the game will be set free. See you tomorrow… HEHE HOHO COUGH COUGH”

You and your fellow prisoners have the night to sweat out a plan. They decide you look like a nerd so they elect you to play the king in tomorrow’s game. One of the prisoners who has been there a while says he has seen the guards play many times before, and that if they are not blocked, they always arrange themselves in the same way. He sketches in the dirt the familiar starting arrangement of chess pieces with rook in the corner then knight, bishop, K, Q, etc. and a row of pawns across.

The other prisoners are looking at you doubtfully and suddenly you wish you had been more of a chess nerd!!

1.) How will you position your pieces for maximum survival?

2.) Is there a way to guarantee the survival of some prisoners? How many?

[Guest]

tbrophy, the first sentence of your spoiler has some merit.

think of some other unique properties of the pawn besides aspirations to royalty.

[Guest]

Well... since you didn't say you could resign, you could sacrifice yourself to win the sruvival of the team, since you have to play a king with maximum skills in chess.

[Guest]

Assuming the guards will always choose the same starting formation . . .

Prisoners choose white, so that they may go first. Then, line up the pawns such that on first move, you essentially have checkmate (fool's mate). Pawn takes pawn in front of King's Bishop, while having a pawn diagonally behind it to force checkmate. Really, piece can be placed to back up that pawn.

[Guest]

If you are really good in playing chess you could start out in the normal starting position and hope you win.

[Guest]

scutill: Wow, i didnt think of that. crap. I will try to change the riddle so that the guards are white and the prisoners have to be on the other "half" of the board. Sorry about that, I give you credit for solving it as written, but the solution I had in mind is not quite so obvious.

jon tam: the guards do set themselves up in the way the riddle says.

noob omega: you do not sacrifice yourself or resign or whatever. Remember, other than the starting positions the game is played as a normal chess game.

[Guest]

Unless I'm misunderstanding the rules,

If the prisoners must choose Black, they have their Queen on F4, a Bishop on H4, and a Rook on F5. The only way to prevent immediate checkmate is Knight to H3, which is followed by Bishop Takes F pawn, check. Then after Knight takes back, Queen Takes Knight, Checkmate.

The prisoners can guarantee to keep all but one of their number.

[Guest]

Or you could start the game with your Knights on D3 and F3. Not sure if this is allowed since 2 Knights checking a king at the same time is impossible in a regular game. But if it is, then all the prisoners will Survive.

[Guest]

I am not sure Scutill's idea works.

I am looking for a way in which the prisoners, choosing to play as Black, pile all their pieces in a formation close to the White first rank. One positions the pieces so that whatever White's first move is, Black is in stalemate, but this seems to be a tall order, especially since the formation must be able to withstand White's firt move and we do not know what White's starting formation will be.

Then at most one prisoner would die.

Edited September 26, 2009 by jerbil

[Guest]

first of all i'd like to apologise in advance because i dont think the spoiler button is working correctly for me, however i think i've came up with a solution for this riddle that allows you to save all of your pieces regardless of what colour you start with.

In this solution i will be assuming that we are the black pieces and our opponent has the white pieces, so here goes....

1. place your black bishop at (b-4)

2. place you queen at (h-4)

3. place any pawn at (e-3)

4. place a rook at (c-6)

5. place the other rook at (f-6)

Here is a website that displays the chess board so you can see what this positions translate to if you are unaware.

http://www.britannica.com/EBchecked/topic-art/318266/97/Position-of-chessmen-at-the-beginning-of-a-game

Hope this solves it, nice riddle though.

[Guest]

But the OP states that the initial positions have no relation to the opening positions in a standard game of chess. Once the prisoners have placed 16 men wherever they wish on the chessboard, then the guards can place 16 men wherever they wish on the rest of the chessboard. Then battle may commence. Whether the first move is played by the prisoners or the guards is entirely up to the prisoners.

[Guest]

I am not sure Scutill's idea works.

I am looking for a way in which the prisoners, choosing to play as Black, pile all their pieces in a formation close to the White first rank. One positions the pieces so that whatever White's first move is, Black is in stalemate, but this seems to be a tall order, especially since the formation must be able to withstand White's firt move and we do not know what White's starting formation will be.

Then at most one prisoner would die.

You got some of it.

"One positions the pieces so that whatever White's first move is, Black is in stalemate" is correct, but how? also, about withstanding whites first move..

it is not an issue because white can only move 2 pieces and they are not in range of black!

[Guest]

That one of the prisoners knows how to set up the initial configuration for a standard game of chess must be sheer window dressing.

I am drawn to the statement that the prisoners know how the guards will initially place themselves provided they are not blocked. However, this can only be of use to the prisoners if they ensure that their starting configuration specifically does not block.

I also realize that there is nothing to prevent the prisoners, playing Black, from placing White in immediate check, which would limit the range of White’s first move. However, I do not immediately see how this might help a “stalemate” resolution to the problem.

Basically, I am stuck on this one. I hope you are going to provide a stunning answer to this intriguing problem.

[Quantum.Mechanic]

1) Can the Guards' side start off in check? That is normally against the rules, but is worth stipulating here.

2) I understand the assumption that the Guards will start in the normal starting formation if possible. However, it seems to be a strategic blunder to do so if they form up last.

[Guest]

Here are some updates:

The guards cannot start in check. (as a further help I will say no check or checkmate ever occurs)

also, as jerbil guessed, One positions the pieces so that whatever White's (guards) first move is, Black (prisoners) are in stalemate. In other words, Black never gets to make a move.

Also, on whites opening move, they can only possibly move 2 pieces. They are surprised by this. Again, of all their 16 pieces, only 2 of them can possibly move. And they are in the exact configuration mentioned in the riddle, although perhaps not how you are thinking.

Again guys, sorry for the confusion. it is my fault. I didnt think of some of the obvious situations you guys came up with. I promise that the answer is decently cool, but a better riddler could have made it way better. I will give the answer soon if no one gets it. By the way, please let me know how I could change it to make it better once you know the answer.

[Guest]

The Prisoners take black but line up on white's side of the board as follows

Knights in the corners, A8 and H8

Followed by Rooks, B8 and G8

Next the Bishops at C8 and F8

Then Queen and King inside at D8 and E8 (order doesn't matter)

Six Pawns will be lined up on B7 through G7 with the remaining two on B6 and G6

With this lineup, no pawns can move forward and they are blocking all moves by the other pieces

I'm assuming then the guards come out and line up in the "normal" starting position on the other side of the board, too stupid to realize they are on the wrong side. The Pawns will be blocking all moves except for the Knights.

Guards move either Knight on first move, Prisoners cannot move, Stalemate, game over.

[Guest]

That makes for a lot of assumptions not in the original post, Magic Man!

Edited September 28, 2009 by jerbil

[Guest]

The Prisoners take black but line up on white's side of the board as follows

Knights in the corners, A8 and H8

Followed by Rooks, B8 and G8

Next the Bishops at C8 and F8

Then Queen and King inside at D8 and E8 (order doesn't matter)

Six Pawns will be lined up on B7 through G7 with the remaining two on B6 and G6

With this lineup, no pawns can move forward and they are blocking all moves by the other pieces

I'm assuming then the guards come out and line up in the "normal" starting position on the other side of the board, too stupid to realize they are on the wrong side. The Pawns will be blocking all moves except for the Knights.

Guards move either Knight on first move, Prisoners cannot move, Stalemate, game over.

You got it!

And again sorry about the confusion, I can see a few ways I could have done this a lot better. oh well. It is hard to try to allow people to think through to the solution in an interesting way without just giving the solution outright. I also wish the site would allow a "redo" or something. Then I could have edited or reposted.

[Guest]

Actually just one assumption jerbil. He says the Guards always line up in the "familiar starting arrangement". I'm assuming that if they can't assemble on the correct side of the board, then they will move to the other side (and perhaps not even realize they are on the wrong side).

If you read his updates in post 16, this is the only scenario that fits.

Edited September 28, 2009 by Magic Man

[Guest]

Solution: Solution: You choose BLACK costumes and arrange yourselves on the WHITE side of the board like this:

• • • • • • • •

• • • • • • • •

• • • • • • • •

• • • • • • • •

• • • • • • • •

• P • • • • P •

• P P P P P P •

N R B Q K B R N Black pieces on white side of board

The guards (white) will set themselves up like they always do on the other side of the board. When white makes the opening move (they can only move the knights), it will be the last move of the game because black cannot move. According to the rules of the riddle, the white team is executed and the prisoners win!

:

[Quantum.Mechanic]

You got it!

And again sorry about the confusion, I can see a few ways I could have done this a lot better. oh well. It is hard to try to allow people to think through to the solution in an interesting way without just giving the solution outright. I also wish the site would allow a "redo" or something. Then I could have edited or reposted.

Hrmmm...What defines which side is the black side and which side is white? Is it not the starting position? Since all normal cues are missing, something else must decide "Black's Pawn Movement Direction", etc. (I'm assuming there are no coordinates on the board, like there are in game discussions.)

So, given no hints, Black can "assume the position" at either end. Under normal chess rules this would determine the pawn direction, would it not?

[Guest]

Hrmmm...What defines which side is the black side and which side is white? Is it not the starting position? Since all normal cues are missing, something else must decide "Black's Pawn Movement Direction", etc. (I'm assuming there are no coordinates on the board, like there are in game discussions.)

So, given no hints, Black can "assume the position" at either end. Under normal chess rules this would determine the pawn direction, would it not?

I should have mentioned that the board is labelled on the side 1-8 and A-H to further define the proper start position, I thought about this but decided it would make the riddle too obvious, so I said it was in a "courtyard" which seemed to me would have defined sides. Again, I was wrong.

Here is the where I got the idea for this riddle. (besides the obvious homage to "hats on death row")

http://orion.math.iastate.edu/burkardt/puzzles/chess_puzzle.html

Perhaps I will repost a different riddle in a few months that is based on this but better thought out. Or one of you guys can. (if you do let me know, I would be interested to see it.)