Same is mine solution - in bash it takes 5s on my VM box, and fails test with time>12000. Sad (

Your code contains undefined behavior:

while (args[j] == args[j - 1] + 1)
{
  j++;
}

you are not checking the bounds of args in this loop. It may read past the end of the array.

In C, there is 100 tests with n choosen randomly between 5k and 100k.