题解 | 进制转换

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

int chartonum(char a)
{
    if(a>='0'&&a<='9')return a-'0';
    else if(a>='A'&&a<='F')return a-'A'+10;
    else if(a>='a'&&a<='f')return a-'a'+10;
    else
    {
        return -1;
    }
}

int main()
{
    string str;
    while(cin>>str)
    {
        str = str.substr(2);
        int len = str.length();
        int sum = 0,j = 0;
        for(int i = len-1;i>=0;i--)
        {
            sum += chartonum(str[i])*pow(16,j++);
        }
        cout<<sum<<endl;
    }


    return 0;
}