为该二进制节点类构造析构函数的正确方法是什么？

Question

class node{

private:
node* parent;
node* leftchild;
node* rightchild;
// etc.... 
}

I don't want to create an infinite cycle with destructor that's why I'm interested how can I make a good constructor for it.

Answer 1

Calling delete on a pointer that is NULL will not call the destructor.
Just set the nodes to NULL in constructor, and only allocate them if they are supposed to exist.

So its safe to delete the sub-objects in the destructor, cause the 'chain' will stop when it reaches a child-node that is NULL .

Example:

#include <iostream>

class Node{
public:
  Node() {
    node = NULL;
  }
  ~Node() {
    std::cout << "Deleting" << std::endl;
    delete node;
  }
  void CreateChildNode() {
    node = new Node();
  }
private:
  Node* node;
};

int main()
{
  Node *n = new Node();
  n->CreateChildNode();
  delete n;
  return 0;
}

Above code snippet will output:
Deleting
Deleting

Answer 2

I would say:

node::~node()
{
    // remove reference to this from neighboor.
    if (leftchild) {
        leftchild->parent = nullptr;
    }
    if (rightchild) {
        rightchild->parent = nullptr;
    }
    if (parent) {
        if (parent->leftchild == this) {
            parent->leftchild = nullptr;
        } else {
            parent->rightchild = nullptr;
        }
    }
}

And the correct smartPointer ( std::shared_ptr / std::weak_ptr or pointer/ std::unique_ptr ) for parent /( leftchild , rightchild ).