题解 | #进制转换#

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

int main() {
    string s;
    int res = 0;
    int base = 1;
    getline(cin, s);
    for (int i = s.size() - 1; i >= 0 && s[i] != 'x'; i--) {
        int now;
        if (s[i] <= '9' && s[i] >= '0') {
            now = s[i] - '0';
        } else {
            switch (s[i]) {
                case 'A':
                    now = 10;
                    break;
                case 'B':
                    now = 11;
                    break;
                case 'C':
                    now = 12;
                    break;
                case 'D':
                    now = 13;
                    break;
                case 'E':
                    now = 14;
                    break;
                case 'F':
                    now = 15;
                    break;
            }
        }
        res += now * base;
        base = base * 16;
    }
    cout << res << endl;
    return 0;
}