大学编程题不懂诶，帮帮我

#include<iostream>
#include<cmath>
using namespace std;
void turn(char* a,int x)
{
    int n=0;
    for(int i=0;i<x;i++)
        if(a[i]<='9')
            n+=(a[i]-'0')*pow(16,(x-i-1));
        else
            n+=(a[i]-'A'+10)*pow(16,(x-i-1));
    cout<<n<<endl;
}
void main(){
  char num[10];
  cin>>num;
  turn(num,strlen(num));
}

#include <stdio.h>
int main()
{
        int n;
        scanf("%X",&n);
        printf("%d",n);
      return 0;
}