题解 | #进制转换#

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


int main() {
    string s;
    cin >> s;
    s = s.substr(2,s.length()-2);
    int count = 0;
    int multi = 1;
    for(int i = 0; i < s.length()-1; ++i)
    {
        multi *= 16;
    }
    for(int i = s.length() - 1; i >= 0; --i)
    {
        s[s.length() - i - 1] - 'A' < 0? count += (s[s.length() - i - 1] - '0') * multi : 
        count += (s[s.length() - i - 1] - 'A' + 10) * multi;
        multi /= 16;
    }
    cout << count <<endl;
}
// 64 位输出请用 printf("%lld")