Comments on: Generating multi-subsets using arithmetic

By: Mark

Mark — Mon, 13 Jul 2009 13:36:34 +0000

You can also use itertools.product for this, at least in Python 2.6 and later:

for x in itertools.product(range(3), repeat=3): print x

I’m not sure multi-subset is a good name, since it suggests that order shouldn’t matter: that is, that {1, 1, 2} should be considered the same as {1, 2, 1}.

By: eliben

eliben — Sun, 12 Jul 2009 17:06:36 +0000

@Steve,

Yep, project Euler would be hard without DP, which was what I used for problem 77 (with a similar algorithm to 76 and 31)

By: Steve

Steve — Sun, 12 Jul 2009 12:33:48 +0000

For Euler problem 77 (and many other ‘counting’ problems) Dynamic Programming is very useful.
http://en.wikipedia.org/wiki/Dynamic_programming
Its worth looking into if you are not already familiar with it.

By: eliben

eliben — Sat, 11 Jul 2009 17:38:14 +0000

@Larry,

This is by design, because an empty subset isn’t interesting. If you need it, just change the initalization of ar in the function to:

ar = [0] + [0] * (length – 1)

By: Larry Hastings

Larry Hastings — Sat, 11 Jul 2009 17:26:55 +0000

Your call to multiselects(2, 3) didn’t generate [0, 0, 0]. Back to the drawing board!