基础练习 十六进制转十进制

注意顺序

#include <iostream>
#include <string>
#include <algorithm>

using namespace std;

int f(int n){
    int sum = 1;
    for (int i = 1; i <= n; i++){
        sum *= 16;
    }
    return sum;
}
int main(){
    unsigned int sum = 0;
    string s;
    cin>> s;
    reverse(s.begin(), s.end());
    for (int i = 0; i <s.size(); i++){
        if (s[i] >= '0' && s[i] <= '9'){
            sum += (s[i] - '0')*f(i);
        }
        if (s[i] >= 'A' && s[i] <= 'F'){
            sum += (s[i] - 'A'+10)*f(i);
        }
    }
    cout << sum << endl;
}