A tool for calculating the big-O time complexity of Java code?

Question

I have a question regarding time complexity (big O notation) for Java software. Is there a way to quickly calculate or test it (or any website that could calculate it for m

Answer 1

I might be solving someone's homework, but the question was begging for a sane solution...

Counting distinct digits in a number requires no strings, sets or regular expressions, just some simple arithmetics.

The following method runs in O(n) time (n = number of digits in the input) and constant space:

int distinctDigits(int num) {
  if (num == 0) {
    return 1;
  }

  boolean[] digits = new boolean[10];

  while (num > 0) {
    digits[num % 10] = true;
    num /= 10;
  }

  int count = 0;
  for (boolean digit : digits) {
    if (digit) {
      count++;
    }
  }

  return count;
}

Making this work for negative numbers is left as an exericse to the reader ;)