Check whether binary tree are same or not?

Problem

Given two binary trees, return true if they are structurally identical -- they are made of nodes with the same values arranged in the same way.

Solution

11. sameTree() Solution (C/C++)
/*
 Given two trees, return true if they are
 structurally identical.
*/
int isIdentical(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 &&
      isIdentical(a->left, b->left) &&
      isIdentical(a->right, b->right)
    );
  }
  // 3. one empty, one not -> false
  else return(false);
}