题解 | 进制转换

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

int trans(char str);
int main() {
    string str;
    getline(cin,str);
    int len = str.length();
    int num = 0;
    for(int i=2 ; i<len ; i++){
        int j = trans(str[i]);
        num += (j * pow(16,len-i-1));
    }
    cout << num;
}
int trans(char ch){//char转int
    switch (ch) {
        case '0':{return 0 ;break;}
        case '1':{return 1 ; break; }
        case '2':{return 2 ; break; }
        case '3':{return 3 ; break; }
        case '4':{return 4 ; break; }
        case '5':{return 5 ; break; }
        case '6':{return 6 ; break; }
        case '7':{return 7 ; break; }
        case '8':{return 8 ; break; }
        case '9':{return 9 ; break; }
        case 'A':{return 10 ; break; }
        case 'B':{return 11 ; break; }
        case 'C':{return 12 ; break; }
        case 'D':{return 13 ; break; }
        case 'E':{return 14 ; break; }
        case 'F':{return 15 ; break; }
        default:{return 0;}
    }
}