I sent two questions on HackerRank and solved both with 25 minutes to spare. I then went through the corner cases. This presented me with a dilemma: I found that their grading script was wrong and wasn't considering one of the constraints imposed on the problem. Should I spend time to find and fix it, or change my answer? I used my abundant time to find the bug, which took 20 minutes. Now my solution was no longer optimal. In my remaining minutes, I commented my code, explaining their bug. I also sent HackerRank a note about it.

The next day, I received word that I would not be making it to the next round. I felt kind of cheated. Perhaps I was just a guinea pig for their problem sets, as other posters have mentioned. However, I didn't expect to at least have a semblance of having a chance at the job for which I solved their technical questions better than they did.

Given an array D of numbers and a target T, count the number of permutations of D [D_a, D_b, D_c] where a < b < c and a + b + c <= T.