5 queens

[Steven D'Aprano]

On Sun, 23 Dec 2007 02:22:38 -0800, cf29 wrote:

> How would you write a function that will populate a list with a list of
> numbers with all the possibilities? For example a list of 3 numbers
> taken among 4 [0,1,2,3] without duplicates. The result should be:
> [0,1,2]
> [0,1,3]
> [0,2,3]
> [1,2,3]

What you are asking for is the combinations of the list, taking 3 
elements at a time. Try using this generator:

def combinations(seq, n):
    if n == 0:
        yield []
    else:
        for i in xrange(len(seq)):
            for cc in combinations(seq[i+1:], n-1):
                yield [seq[i]]+cc


>>> for c in combinations(range(4), 3):
...     print c
...
[0, 1, 2]
[0, 1, 3]
[0, 2, 3]
[1, 2, 3]


-- 
Steven