Unusual Speed Difference between Python and C++

Question

I recently wrote a short algorithm to calculate happy numbers in python. The program allows you to pick an upper bound and it will determine all the happy numbers below it.

Answer 1

Well, I also gave it a once-over. I didn't test or even compile, though.

General rules for numerical programs:

• Never process numbers as text. That's what makes lesser languages than Python slow, so if you do it in C, the program will be slower than Python.

• Don't use data structures if you can avoid them. You were building an array just to add the numbers up. Better keep a running total.

• Keep a copy of the STL reference open so you can use it rather than writing your own functions.

---

void calcMain(int upperBound)
{
    vector known;
    for(int i = 0; i <= upperBound; i++)
    {
        int current = i;
        vector history;
        do
        {
            squaresum = 0
            for ( ; current; current /= 10 )
            {
                int digit = current % 10;
                squaresum += digit * digit;
            }
            current = squaresum;
            history.push_back(current);
        } while ( ! count(history.begin(), history.end() - 1, current) );

        if(current == 1)
        {
            known.push_back(i);
            //cout << i << "\t";
        }

    }
    //cout << "\n\n";
}