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;

}