Talk:N-queens problem

From Rosetta Code

Tcl: All Solutions[edit]

Is the goal to find one solution, or all solutions? -- 19:59, 12 September 2009 (UTC)

I've put up code to find all solutions; finding just one is a trivial adaptation of that (stop iterating after the first solution is found...) —Donal Fellows 20:37, 12 September 2009 (UTC)
I read the task's requirements differently.   It said to   Solve the eight queens puzzle,   and once solved, stopped looking for more solutions.   I didn't see any point in providing multiple answers.   Of the   92   solutions on an   8x8   board,   12   are fundamental solutions --- and just sifting (choosing which ones to display) those out (I thought) isn't part of the task's requirement.   ··· And if the answers are an ASCII art depiction of the chessboard, the amount of output would be greatly compounded.   -- Gerard Schildberger (talk) 21:57, 6 May 2016 (UTC)

Python permission[edit]

I thought I might copy the email trail where I got permission to post a Python solution from its original author:

Re: 8-Queens
Steve Howell <[email protected]>
Mon, 14 Sep 2009 23:07:09 -0700 (PDT)
Paddy McCarthy <[email protected]>


--- On Mon, 9/14/09, Paddy McCarthy <[email protected]> wrote:

    From: Paddy McCarthy <[email protected]>
    Subject: Re: 8-Queens
    To: "Steve Howell" <[email protected]>
    Date: Monday, September 14, 2009, 11:54 AM

    Ta very much. It's in place.

    Steve Howell wrote:
>     Please do, thank you.
>     Sent from my iPhone
>     On Sep 13, 2009, at 10:43 AM, Paddy McCarthy <[email protected]> wrote:
>>     Hi,
>>     I wondered if you would allow me to submit your 8-Queens solution to  Rosetta  Code ?
>>     -- Donald 'Paddy' McCarthy

--Paddy3118 04:28, 6 September 2010 (UTC)

Removing existing C code: webbug?[edit]

I added a C solution, then realized the existing C example is sending results to some http server. This amounts to a web bug, I'm removing it, until the intent of the webbug can be clarified and justified --Ledrug 03:34, 6 July 2011 (UTC)

Apparently the ip address is somewhere in germany, on a machine owned by Also, a google search finds which suggests that this is a machine that at one point was owned by Leonie Schöller. Then again, suggests a machine owned by someone named Manuela. --Rdm 04:44, 6 July 2011 (UTC)
Whoever it was, that was a fairly odd thing to do: it's not like code here gets compiled and run very often-- —Ledrug 05:25, 6 July 2011 (UTC)

REXX mistake[edit]

I'm not familiar with REXX, nor do I have any idea how to fix it; however, the two outputs produced (for board sizes 8 and 20) are both unsuccessful attempts at nqueens. In the 8x8 board, rows 4 and 6 (1-up) have queens in diagonal contradiction; in the 20x20 board, (at least, didn't bother to check more) rows 1 and 6 have queens in diagonal contradiction.

Anyone familiar enough to know whether this is a printing error or a solving error, and either way, how to fix it?

It was my mistake, I had cut and pasted the solutions from an earlier version, corrected the REXX program, but neglected to updated the outputs.   I re-ran the REXX program and pasted the chessboard to the OUTPUT sections. -- Gerard Schildberger (talk) 16:39, 22 July 2013 (UTC)

What about profiling?[edit]

When doing the Erlang version I thought it would be much faster to calculate diagonals in advance. It did not help at all. I should have profiled before changing the code.

Is there a task on Rosettacode that looks at profiling? Similar to Time_a_function, but for several functions in a task. User:bengt Sat Dec 7 13:23:33 CET 2013


I am not known for my compact code, but I have a script in Pari/GP. Not optimized to any extent. Just contact me.--Billymacc (talk) 12:42, 14 October 2017 (UTC)