Problem #43

I was kind of lazy with this, but finally got around to re-creating my code for it. Here it is, it runs in 4.187 seconds on my computer.

#include <iostream>
#include <ctime>
#include <algorithm>
#include <string>
#include <cmath>

using namespace std;

bool isCompatible (string);
bool checkDivisibility (int, int, int, int);

int main() 
{
    clock_t start = clock();
    long long int total = 0;
    long long int holder = 0;
    string str;

    int num[]={0, 1, 2, 3, 4, 5, 6, 7, 8, 9};

    sort (num, num + 10);

    do {
        str.clear ();
        for (int i = 0; i < 10; i++)
            str += num[i] + '0';
        if (isCompatible (str))
        {
            holder = 0;
            for (int i = 0; i < 10; i++)
                holder += (str[str.size () - 1 - i] - '0') * pow (10, static_cast<double>(i));
            total += holder;
        }
    } while ( next_permutation (num, num + 10));


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

    system("pause");
    return 0;
}

bool isCompatible (string str)
{
    if ((str[3] - '0') % 2 == 0)
        if (((str[2] - '0') + (str[3] - '0') + (str[4] - '0')) % 3 == 0)
            if ((str[5] - '0') % 5 == 0)
                if (checkDivisibility (str[4] - '0', str[5] - '0', str[6] - '0', 7))
                    if (checkDivisibility (str[5] - '0', str[6] - '0', str[7] - '0', 11))
                        if (checkDivisibility (str[6] - '0', str[7] - '0', str[8] - '0', 13))
                            if (checkDivisibility (str[7] - '0', str[8] - '0', str[9] - '0', 17))
                                return true;
                            else
                                return false;
                        else
                            return false;
                    else
                        return false;
                else
                    return false;
            else
                return false;
        else
            return false;
    else
        return false;
}

bool checkDivisibility (int a, int b, int c, int d)
{
    if ((a * 100 + b * 10 + c) % d == 0)
        return true;
    return false;
}