Re: [xsl] n-queens?

[Hermann Stamm-Wilbrandt <STAMMW@xxxxxxxxxx>]

> This puzzle, although interesting, is commonly given to beginning
> programming students.
>
Yes, but I posted here because of "XSLT 1.0 + exslt:node-set()" solution
and the two questions I have (Muenchian grouping / functional style).

> I remember facing it myself. One I have never seen solved
> are the number of boards where less than eight queens is the maximum.
>
Please be more precise on what you count as "a board".
Does the board contain less than 8 queens for your problem?
Or does the board always contain 8 queens, some threatening another?

In the latter case the answer is:
(64 choose 8) - 92 = 4426165368


Long ago I posted some queen-puzzles on a (German language) chess forum.
Here you can see a position with 5 queens threatening all fields:
http://www.schachmatt.de/69-schachraetsel/2764-3xdamen-uberdeckung.html#post2
2269

It is not possible to threaten all fields with only 4 queens.
So for the first problem the count of all positions with 5, 6 and 7 queens
threatening all fields seem to be what you are interested in, right?


Mit besten Gruessen / Best wishes,

Hermann Stamm-Wilbrandt
Level 3 support for XML Compiler team and Fixpack team lead
WebSphere DataPower SOA Appliances
https://www.ibm.com/developerworks/mydeveloperworks/blogs/HermannSW/
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  From:       "Mark" <mark@xxxxxxxxxxxx>

  To:         <xsl-list@xxxxxxxxxxxxxxxxxxxxxx>,

  Date:       04/21/2012 08:25 PM

  Subject:    Re: [xsl] n-queens?






This puzzle, although interesting, is commonly given to beginning
programming students. I remember facing it myself. One I have never seen
solved are the number of boards where less than eight queens is the
maximum.
Mark

-----Original Message-----
From: Ivan Shmakov
Sent: Saturday, April 21, 2012 8:26 AM
To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
Cc: Ivan Shmakov
Subject: Re: [xsl] n-queens?

>>>>> Michael Hopwood <michael@xxxxxxxxxxx> writes:

> I'm no chess OR maths expert but - surely they are not actually chess
> queens if any two of the same colour can threaten each other?  The
> puzzle using actual chess queens, at least one of which is of the
> other colour, would look quite different...

AIUI, for the purposes of this puzzle, /each/ of the queens is
assumed to be of its own distinct colour.

--cut: http://en.wikipedia.org/wiki/Eight_queens_puzzle --
    The eight queens puzzle is the problem of placing eight chess queens
    on an 8W8 chessboard so that no two queens attack each other.  Thus,
    a solution requires that no two queens share the same row, column,
    or diagonal.  The eight queens puzzle is an example of the more
    general n-queens problem of placing n queens on an nWn chessboard,
    where solutions exist for all natural numbers n with the exception
    of 2 and 3.
--cut: http://en.wikipedia.org/wiki/Eight_queens_puzzle --

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