题解 | #进制转换#

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

int main() {
    string str;
    cin >> str;
    int pos = 0,tenNum = 0;
    for(int i = str.length()-1;i > 1;i--,pos++){
        if(str[i] >= '0' && str[i] <= '9'){
            tenNum += (str[i]-48)*pow(16,pos);
        }
        if(str[i] >= 'a' && str[i] <= 'f'){
            int tmp = (int)str[i] - 97 + 10;
            tenNum += tmp*pow(16,pos);
        }else if(str[i] >= 'A' && str[i] <= 'F'){
            int tmp = (int)str[i] - 65 + 10;
            tenNum += tmp*pow(16,pos);
        }
    }
    cout << tenNum << endl;
}
// 64 位输出请用 printf("%lld")