#include<stdio.h>
2
3 void reverse(char[]);
4
5 int main(void)
6 {
7     char s[] = "abcd";
8     reverse(s);
9     printf("%s\n", s);
10     return 0;
11 }
12
13 void reverse(char s[])
14 {
15     static int i = 0;
16     static int j = 0;
17     if(s[j++])
18     reverse(s);
19     s[i++] = s[j - 1];
20     s[i] = '\0';
21
22
23 }

交换没有临时变量, 肯定会丢数据,
s[i] = '/0' 把数据都清了

不清楚你的递归逻辑, 你得说清楚

#include<stdio.h>

 void reverse(char[]);

 int main(void)
 {
     char s[] = "abcd";
     reverse(s);
     printf("s=%s\n", s);
     return 0;
 }

 void reverse(char s[])
 {
    static char a[5];
    static int i = 0;
    static int j = 0;
    if(*(s+j))
    {
        j++;
        reverse(s);
    }
    j--;
    a[i] = *(s+j);   
    if(i==4)
    {
        int k;
        a[i]='\0';
        for(k=0;k<i;k++)
            *(s+k)=a[k];
        *(s+i)=a[i];   
    }
    i++;
    }