我写了一个函数来搜索二叉搜索树，但是我有逻辑问题：当我插入一些值时，我有一个 2 级的树，最后一级（在本例中为 2 级）未满（满是它没有所有子节点）它返回 3，而不是 2：

// --- Definition of depth()
template<typename DataType>
int BST<DataType>::depth()
{

  int counter = 0; 

  return Auxdepth(counter, myRoot);

}


// --- Definition of Auxdepth()
template<typename Datatype>
int BST<Datatype>::Auxdepth(int &counter, BinNodePointer subtree)
{
 //BinNodePointer parameter is myRoot, which is the root node
int a;
int b; 

if(empty()) return -1;// garbage value

if(subtree->left == 0 && subtree->right == 0)
    return counter;

else if(subtree->left == 0){
    int x = counter++;
    a= Auxdepth(x,subtree->right);
    return a;
}

else if(subtree->right == 0){
    int x = counter++;
    a = Auxdepth(x,subtree->left);
    return a;
}

if(subtree != 0) { // Recursion
    int x = counter + 1;
    cout << "This is x " << x << endl;
    a = Auxdepth(x, subtree->left);
    b = Auxdepth(x, subtree->right);

            if(a > b) return a;
            else return b;
    }
} 

注意：深度功能只是为了更友好。谁能告诉我我的错误在哪里？