Problem #37

This one is kind of like the circular primes...quite simple really.

#include <iostream>
#include <string>
#include <cmath>

using namespace std;

bool isPrime (int);
int truncLeft (int);
int truncRight (int);
bool checkLeft (int);
bool checkRight (int);


int main()
{
    int total = 0;

    for (unsigned int i = 10; i < 1000000; i++)
        if (isPrime (i))
            if (checkLeft (i) == true && checkRight (i) == true)
                total+=i;

    cout << total << endl;

    system ("pause");
    return 0;
}

bool isPrime (int num)  
{  
    if (num == 0 || num == 1)
        return false;

    if (num == 2 || num == 3)  
        return true;  
  
    for (unsigned int i = 2; i < static_cast<int> (sqrt (static_cast<double> (num))) + 1; i++)  
        if (num % i == 0)  
            return false;  
    return true;  
}  

int truncLeft (int num)
{
    char buffer[32];
    string str, str2;

    sprintf (buffer, "%i", num);
    str = buffer;
    
    str2 = str.substr (1);
    
    return atoi (str2.c_str ());
}

int truncRight (int num)
{
    char buffer[32];
    string str, str2;

    sprintf (buffer, "%i", num);
    str = buffer;
    
    str2 = str.substr (0, str.size () - 1);
    
    return atoi (str2.c_str ());
}

bool checkLeft (int num)
{
    while (num > 10)
    {
        num = truncLeft (num);
        if (!isPrime (num))
            return false;
    }
    return true;
}

bool checkRight (int num)
{
    while (num > 10)
    {
        num = truncRight (num);
        if (!isPrime (num))
            return false;
    }
    return true;
}