题解 | #进制转换#

#include <bits/stdc++.h>
#include <cctype>
using namespace std;

int main() {
   unordered_map<char,int> map;
   map['A'] = 10;
   map['B'] = 11;
   map['C'] = 12;
   map['D'] = 13;
   map['E'] = 14;
   map['F'] = 15;

   string str1;
   getline(cin,str1);
   str1 = str1.substr(2,str1.size() - 2);
   long long res = 0l;
   int i = 0;
   for(auto it = str1.rbegin(); it != str1.rend(); it++,i++){
        if(!isdigit(*it)){
            res += map[*it]*pow(16,i);
        }else {
            res += (*it - '0') * pow(16,i); 
        }
   }

    cout << res << endl;
    return 0;
}
// 64 位输出请用 printf("%lld")