I just spent quite a while debugging my solution to C, which I was confident was correct but failed on test 5 due to a runtime error. It turns out that it was a stack overflow error, and after I increased the stack size, my solution passed (original, with increased stack size). I feel that I should have gotten credit for my original solution during the contest since it would have passed within the given time and memory constraints and only failed due to a restriction in the judging environment.