题解 | #进制转换#

#include <iostream>

using namespace std;
int main()
{
    string str;
    cin >> str;
    int len = str.length(), hex = 1, sum = 0;
    for (int i = len - 1; i > 1; i--)
    {
        if (str[i] >= 'A')
        {
            sum += (str[i] - 'A' + 10) * hex;
        }
        else
        {
            sum += (str[i]-'0') * hex;  //字符数字转换为整数： '2'-'0'
        }
        hex *= 16;
    }
    cout << sum << endl;
}