水题
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main(){
vector<int> a(4);
cin >> a[0] >> a[1]>>a[2]>>a[3];
string str;
cin >> str;
int res = 0;
for(int i = 0 ; i < str.length(); ++ i) res+=a[str[i]-‘0‘-1];
cout<<res<<endl;
}
Codeforces Round #249 (Div. 2) A. Black Square,布布扣,bubuko.com
Codeforces Round #249 (Div. 2) A. Black Square
原文：http://www.cnblogs.com/xiongqiangcs/p/3786254.html