Kiyoura's Reverse String Challenge Solution

kiyoura.c

#include <stdio.h>

int main (void) {
 char str[] = "password";
 int i = 0;
 /* for pointer arithmetic */
 char *ptr = str;
 while (*ptr && (*ptr += (i++)))
  ptr++;
 printf("%s\n", str);

 i = 0;
 ptr = str; // repoint to beginning of string
 while(*ptr && (*ptr -= (i++)))
  ptr++;
 printf("%s\n", str);

 return 0;
}