[Algorithm/Data Structure] Tree C/C++ example code (+ Mirror Tree)

#include <stdio.h>
#include <stdlib.h>
 
typedef int Element;
 
class Node
{
public:
    int id;
    Element elem;
    Node* left;
    Node* right;
 
    Node() : Node(0, 0, nullptr, nullptr) {};
    Node(int id, Element elem) : Node(id, elem, nullptr, nullptr) {};
    Node(int id, Element elem, Node* left, Node* right) : id(id), elem(elem), left(left), right(right) {}
    virtual ~Node() 
    {
        printf("Node %d Deleted \n", id);
        delete left;
        delete right;
    }
    void preorder()
    {
        printf(" %d", elem);
        if (left) left->preorder();
        if (right) right->preorder();
    }
    void inorder()
    {
        if (left) left->preorder();
        printf(" %d", elem);
        if (right) right->preorder();
    }
    void postorder()
    {
        if (left) left->preorder();
        if (right) right->preorder();
        printf(" %d", elem);
    }
    Node* search_child(int id)
    {
        if (this->id == id)
            return this;
 
        Node* node = nullptr;
        if (left != nullptr)
            node = left->search_child(id);
        if (node == nullptr && right != nullptr)
            node = right->search_child(id);
 
        return node;
    }
};
 
Node* mirror_tree(Node* node)
{
    Node* left = nullptr;
    if (node->right)
        left = mirror_tree(node->right);
 
    Node* r = nullptr;
    if (node->left)
        r = mirror_tree(node->left);
 
    return new Node(node->id, node->elem, left, r);
}
 
int main()
{
    // init tree (bottom-to-top)
    const int NODE_LEN = 6;
    Node* node[NODE_LEN];
    for (int i = 0; i < NODE_LEN; i++)
        node[i] = nullptr;
 
    node[4] = new Node(4, 4);
    node[5] = new Node(5, 5);
    node[2] = new Node(2, 2);
    node[3] = new Node(3, 3, node[4], node[5]);
    node[1] = new Node(1, 1, node[2], node[3]);
    Node* root = node[1];
 
    // test preorder()
    printf("preorder : ");
    root->preorder();
    printf("\n");
 
    // test preorder() of mirror_tree
    Node* mirror_root = mirror_tree(root);
    printf("preorder : ");
    mirror_root->preorder();
    printf("\n");
 
    // test search_child()
    Node* child = nullptr;
    child = root->search_child(2);
    if (child != nullptr)
        printf("id : %d \n", child->id);
    else
        printf("id : null \n");
 
    child = root->search_child(5);
    if (child != nullptr)
        printf("id : %d \n", child->id);
    else
        printf("id : null \n");
    
    child = root->search_child(6);
    if (child != nullptr)
        printf("id : %d \n", child->id);
    else
        printf("id : null \n");
 
    printf("Delete original tree \n");
    delete root;
    printf("Delete mirror_tree \n");
    delete mirror_root;
    return 0;
}
/*
original tree : 
  1
2   3
   4 5
preorder : 12345


mirror_tree : 
   1
 3   2
5 4
preorder : 13542

*/