求C程序：输入字符型16进制,以回车结束，转换输出10进制

#include<stdio.h>
int main()
{
int base=16,n;
char a[32];
long s=0;
int i=0;
scanf("%c",&a[i]);
while('0'<=a[i]&&a[i]<='9'||'A'<=a[i]&&a[i]<='F')
{
i++;
scanf("%c",&a[i]);
}
n=1;
while(--i>=0)
{
if('0'<=a[i]&&a[i]<='9')s+=(a[i]-'0')*n;
if('A'<=a[i]&&a[i]<='F')s+=(a[i]-'A'+10)*n;
n*=base;
}
printf("%ld\n",s);
return 0;
}

#include <stdio.h>
main()
{
int a;
scanf("%x",&a);
printf("%d",a);
}

#include"stdio.h"
int swit(char ch)
{
int n;
if(ch>='0'&&ch<='9')
n=ch-'0';