8 Queens Problem

[Geoff Bien]

<Simon.Foster at smiths-aerospace.com> wrote in message
news:mailman.1026221774.20130.python-list at python.org...
>
>
> Just For Fun!
>
> I've been working on a solution to the eigth queens puzzle.
> Here is my attempt.  There's a solution in Scheme in SICP
> which takes only 13 lines.  Can anyone come up with a shorter
> solution in Python, without any of the obvious silliness?
>

import string

def queens(n,lr,vert,rl,cols):
  lr, rl  = lr >> 1, rl << 1
  if len(cols)==n:
      print 'Solution: ', string.join(cols,', ')
  for col, bitmask in [ (i+1, 0x01 << i) for i in range(n)]:
     if not (bitmask & (lr | vert | rl)):
         queens(n, lr | bitmask, vert | bitmask, rl | bitmask, cols+[`col`])

queens(8,0,0,0,[])