编辑代码

#include <stdio.h>
#include <string.h>
int main () {
    
    char a[20],tmp;
    printf("Input a string:");
    gets(a);
    char *p = NULL, *q = NULL;
    p = q = a;
    q += strlen(a) - 1;
    while(p < q)
    {
        tmp = *p;
        *p++ = *q;
        *q-- = tmp;
    }
    puts(a);
	return 0;
}