winning the battle but...
battled for an embarrasingly long time with this problem for coderbyte:
Using the JavaScript language, have the function PermutationStep(num) take the num parameter being passed and return the next number greater than num using the same digits. For example: if num is 123 return 132, if it's 12453 return 12534. If a number has no greater permutations, return -1 (ie. 999).
Input = 11121 Output = 11211 Input = 41352 Output = 41523
My original solution didn't take too terribly long, and it was able to pass all my test cases, but then coderbyte's response informed me that it failed for a really exhaustive case such as 897654321. I was exceeding my stack limit on that case, so I rethought ways to keep the permutations to the minimum. Really happy I that I pulled through it because the result also runs much faster.