题解 | 进制转换

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

int main() {
    string s;
    cin >> s;
    int num = 0;
    for(int i = 2; i < s.length(); i ++){
        if(s[i] >= 65 && s[i] <= 70){
            num += (s[i] - 55) * (pow(16 , (s.length() - i - 1)));
            // cout << (s[i] - 55)<<endl;
            // cout << (pow(16 , (s.length() - i))) << endl;;
        }
        else{
            num += (int(s[i]) - 48)* (pow(16 , (s.length() - i - 1)));
            
        }
        // cout << num <<endl;
    }
    cout << num;
    return 0;
}
// 64 位输出请用 printf("%lld")