// todo - write strlen


// strcmp function
int strcmp(char *s1, char *s2) {
  if (s1 == NULL || s2 == NULL) return 0;

  int diff, i;
  for(i=0; s1[i] != '\0' && s2[i] != '\0'; i++) {
    diff = s1[i] - s2[i];
    if (diff != 0) return diff;
  }

  // if here, then s1 and s2 were equal up to the end of one of them
  if (s1[i] == '\0' && s2[i] == '\0') return 0;
  
  if (s1[i] == '\0') return -1;
  else return 1;
}