基础练习 十六进制转十进制

#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;
}