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Chess puzzle I found in my dad's old book

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Re: Chess puzzle I found in my dad's old book

#21

Post by maest »

dwa3592 wrote: post #11
ra0x3 wrote: post #6

Wait, the instructions are a little ambiguous. I clicked "Solution" and it has the dark-squared bishop on a white square! XD Should maybe update the instructions to clarify that the dark-squared bishop is not constrained to dark squares.

that's exactly what happened to me. I ended up spending so much time thinking black bishop can only go to black squares. and agreed this is a bit ambiguous.

You can rotate any solution by 90 degrees, which would toggle the square colour of your bishop, so it doesn't ultimately matter.

Re: Chess puzzle I found in my dad's old book

#22

Post by pimlottc »

Please don’t use red and green for the colors in the “check” mode, it’s hard to tell apart for colorblind people (especially against the partially shaded black squares).

In fact, there isn’t really a need for two colors. Just color the squares that are threatened by the pieces and leave the rest blank. The meaning will be obvious.

Re: Chess puzzle I found in my dad's old book

#23

Post by yunwal »

jhncls wrote: post #10
tromp wrote: post #5

> The task is to place four black queens and one black bishop on the chessboard so that there is no square not under their attack. In other words, after arranging the five black pieces, it must be impossible to place the white king anywhere without it being in checkmate. That last word should be "check". not "checkmate". A king next to an unprotected queen will be in check but not checkmate as it can capture the quee…

Although unlikely, maybe there exists a solution where all black pieces are protected?

If there is, it's not listed as the solution on the puzzle website

Re: Chess puzzle I found in my dad's old book

#24

Post by aidenn0 »

hatthew wrote: post #19

I solved it with this, a pleasingly symmetric solution. I was surprised that a solution exists with all the queens in a row. . . . . . . . . . . . . . . . Q . . B . . . . . . . . . . Q . . . . . . . . . . . . . Q . . . . . . . . . . . . . Q . . . . . .

More surprising to me is that there's a solution with no pieces on black.

Re: Chess puzzle I found in my dad's old book

#25

Post by archargelod »

hatthew wrote: post #19

I solved it with this, a pleasingly symmetric solution. I was surprised that a solution exists with all the queens in a row. . . . . . . . . . . . . . . . Q . . B . . . . . . . . . . Q . . . . . . . . . . . . . Q . . . . . . . . . . . . . Q . . . . . .

I found this solution (actually, it's 4 solutions, each B is a different Bishop placement and at the same time it's the only 4 spots on the board not covered by queens):

    . B . . . . . .
    . . . . . . Q .
    . . . B . . . .
    Q . . . . . . .
    . . . . . B . .
    . . Q . . . . .
    . . . . . . . B
    . . . . Q . . .

Re: Chess puzzle I found in my dad's old book

#26

Post by coherentpony »

> The task is to place four black queens and one black bishop on the chessboard so that there is no square not under their attack

> In other words, after arranging the five black pieces, it must be impossible to place the white king anywhere without it being in checkmate.

These two sentences mean very different things in the normal rules of chess. And if you replace the word “checkmate” with the word “check” in the second sentence it still doesn’t mean the same thing as the first sentence.

The first sentence implies that all the pieces must be defended.

Edit: Eh, I guess it depends on how you view the word “attack” since all the pieces are the same colour.

Re: Chess puzzle I found in my dad's old book

#27

Post by aaron695 »

sobellian wrote: post #16
dllu wrote: post #3

Neat. Surprisingly, there are 388 solutions, and a lot of them look rather unintuitive. ........ ...Q.... ........ ........ .....Q.. ........ ........ Q..B..Q. Q....... ........ ........ ........ ..QQB..Q ........ ........ ........ My original intuition was to place the queens on unique rows and columns to cover as much as possible but it turns out there are solutions with three of them on the same row. Python script…

I used CP-SAT to enumerate the solutions. A heuristic for "interesting" solutions is those which only admit one valid bishop placement. For example: ........ Q..B..Q. ........ ........ .......Q ........ ........ ...Q.... Where the bishop lies at the intersection of three queens' horizontal attacks. With these queens, no other bishop placement works.

[dead]

Re: Chess puzzle I found in my dad's old book

#28

Post by nojs »

tromp wrote: post #5

> The task is to place four black queens and one black bishop on the chessboard so that there is no square not under their attack. In other words, after arranging the five black pieces, it must be impossible to place the white king anywhere without it being in checkmate. That last word should be "check". not "checkmate". A king next to an unprotected queen will be in check but not checkmate as it can capture the quee…

Yeah, the solution given is actually wrong as stated!
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