Problem #40

Heres #40. There are ways to speed this up, like loop through it all and count the numbers as they are found (instead of storing them all in a string), then when you have found the last one break out of the loop. That would save on memory, and speed, but I decided to go the easy way (and it runs to completion in 1.657 seconds, quick enough for me).

#include <iostream>
#include <string>
#include <ctime>

using namespace std;

int main() 
{
    clock_t start = clock();
    int total = 0;
    char buffer[32];
    string str;

    for (unsigned int i = 0; i < 1000000; i++)
    {
        sprintf (buffer, "%i", i);
        str += buffer;
    }

    total = (str[1] - '0') * (str[10] - '0') * (str[100] - '0') * (str[1000] - '0') * (str[10000] - '0') * (str[100000] - '0') * (str[1000000] - '0');

    cout << total << endl 
         << "Process took " << (static_cast<double> (clock()) - start) / CLOCKS_PER_SEC << " seconds." << endl;
    system("pause");
    return 0;
}