poj 3589 Number-guessing Game

#include <iostream>
#include <string>
using namespace std;

int main()
{
string num1, num2;
int a, b, tc, i, j;
cin >> tc;
while (tc--)
{
cin >> num1 >> num2;
a = b = 0;
for (i = 0; i < 4; i++)
for (j = 0; j < 4; j++)
{
if (num1[i] == num2[j])
{
if (i == j)
a++;
else
b++;
}
}
cout << a << "A" << b << "B" << endl;
}

system("pause");
}