练习 4-13 编写一个递归版本的 reverse(s)函数，以将字符串 s 倒置

#include <stdio.h>


int swap(char *s,char *p)
{
   int i = 0;
   char temp;


   if(*++p != '\0')
      i = swap(s,p);
   if((s+i) <= (--p))
   {
      temp = *(p);
      *(p) = *(s+i);
 *(s+i) = temp;
   }
   return ++i;
}


char *reverse(char *s)
{
   char *p,*q;


   q = p = s;
   swap(q,p);
   return s;
}


int main(void)
{
   char s[] = "I want eat fish!";


   printf("%s\n",reverse(s));
   return 0;
}