一 ##全局变量max,mid,min##

int max, mid, min;
int MAXMIN(int a, int b, int c)
{
 max = a;
    min = a;
    if (max < b)
        max = b;
    if (max < c)
        max = c;
    if (min > b)
        min = b;
    if (min > c)
        min = c;
    mid = a + b + c - max - min;    
}

二 指针

void MAXMIN(int *a,int *b,int *c)
{
   int max,min,mid;
    max = *a;
    min = *a;
    if (max < *b)
        max = *b;
    if (max < *c)
        max = *c;
    if (min > *b)
        min = *b;
    if (min > *c)
        min = *c;
    mid = *a + *b + *c - max - min;
    *a=max;*b=mid;*c=min;
 //   printf("%p \n%p\n%p",&a,&b,&c);
  //  printf("%d\n%d\n%d\n",a,b,c);
}
    MAXMIN(&a, &b,&c );
printf("s:%d %d %d",a,b,c);