JavaScript: Working out permutations

Andy@DP · 02-14-2009, 08:05 AM

I'm looking to create a JavaScript script that can work out permutations, no duplicates or singles, so an array of numbers with 0, 1, 2 and 3 should return:

Code:

01, 02, 03, 12, 13, 23
012, 013, 023, 123
0123

The actual script will do something once it reaches a permutation, so 23 would actually be used to access two items in an array at positions 2 and 3 and return a value based on these values.

Now recursion is a topic I have never got my head around and I think it's probably going to be the answer to this post so any help would be appreciated.

ntubski · 02-17-2009, 11:17 AM

What you are asking is more like power sets.

Looking at the order in which you wrote the numbers it looks like you already have the algorithm in your head: it's just a simple loop starting with 01 you add 1 to the last digit each time until it reaches the max, then you carry over to next digit.

Andy@DP · 02-17-2009, 11:56 AM

No way - I didn't even see the pattern in the numbers that I wrote until you mentioned it.
That will give me something to work off, it should be simple enough to code that.

Cheers!