TADM2E 3.21

bool compare(struct node* a, struct node* b) {

  // 1. both empty -> true
  if (a==NULL && b==NULL) return(true);   

// 2. both non-empty -> compare them
  else if (a!=NULL && b!=NULL) {
    return(
      a->data == b->data &&
      compare(a->left, b->left) &&
      compare(a->right, b->right)
    );
  }

  // 3. one empty, one not -> false
  else return(false);
}  

--Max 06:41, 25 June 2010 (EDT)