为什么二叉树中的根变量是节点的指针而不是节点本身？

Question

I am trying to implement a Binary Tree in C++ and was going through some tutorials online to learn more about it.

I noticed that all tutorials mention that the root variable of the Binary Tree should be a pointer to the root node and not the node itself. Example code:

struct Node {
  int data;
  Node *left, *right;
};

class BinaryTree {
  private:
     Node *root;
};

Why not make the root variable Node root instead and when I insert a node in the binary tree I can assign values to the root?

Answer 1

Since the root node is also a node, it can be deleted. If it is not a pointer, you would have to start copying nodes instead of just moving pointers.

It could also be nullptr if the tree is empty