问题 E: Double Password

PS:关键点，排列组合

#include<iostream>
using namespace std;
int main()
{
	string a, b;
	cin >> a >> b;
	int n = 1;
	for (int i = 0; i < 4; i++) {
		if (a[i] == b[i]) {
			n *= 1;
		}
		else {
			n *= 2;
		}
	}
	cout << n;
	return 0;
}