Hi all,
given a sequence of n elements i need to generate all possible
permutations of length k <= n.
I found an elegant way to do this recursively:
def comb(items, n):
if n==0: yield []
else:
for i in xrange(len(items)):
for cc in comb(items[i+1:],n-1):
yield [items[i]]+cc
However, this is way too slow for my needs. I try to use this to
generate all possible 5 card poker hands, but this takes around 17
seconds on an Athlon 2200. That's a 2 orders of magnitude too slow for
my needs.
I am familiar with writing Python extensions in C++, but I will not do
this until I am confident that it is the only way to get the speed I need.
Any of you excellent sirs have any suggestions on how I can speed this up?
Please find attached an example script that executes and times the poker
hand generation.
--
Frode, SIM
"Any fool can write code that a computer can understand.
Good programmers write code that humans can understand"
import sys
from timeit import Timer
def comb(items, n):
if n==0: yield []
else:
for i in xrange(len(items)):
for cc in comb(items[i+1:],n-1):
yield [items[i]]+cc
def test():
cards = range(52)
for hand in comb(cards, 5):
"do something with the hand"
def main(argv):
t = Timer("test()", "from __main__ import test")
print t.timeit(1)
if __name__=="__main__":
sys.exit(main(sys.argv[1:]))
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