Making grandchild of root null , the right way in C++

Question

I am trying to create a multiway tree with the following code in C++. As of now, it is more like a sample piece of code.

I wish to do the following with this piece of code(and I am able to get the desired result):

1. Create a struct Node of two members : value(of the node) and array of children of the node.
2. Make 'root's value = 5
3. Make the children's values equal to 10,20,30 & 40
4. Make the children of children's values equal to null(=0);

I am getting the desired output , but what I want to know is if I am doing it the right way.

Thanks, in advance.

//multinode tree
#include<iostream>
#define null 0

struct Node
{
    int value;
    Node *child[4]; 
};

void display(Node *root){
    if(root==null)
        return;
    else{

        std::cout<<root->value<<" ";
        if(root->child[0]!=null)
            for (int i=0;i<4;i++)
            {
                if(root->child[i]!=null)
                    display(root->child[i]);

            }
    }
}

int main()
{
    Node *root=new Node;
    Node *test=null;
    root->value=5;
    int values[]={10,20,30,40};
    int i=0;
    for (i=0;i<4;i++)
    {
        Node *temp=new Node;
        temp->value=values[i];
        root->child[i]=temp;
        for (int j=0;j<4;j++)
        {
            root->child[i]->child[j]=null;
        }
        std::cout<<"Root value "<<root->child[i]->value<<"\n\n ";
    }
    std::cout<<"\n\n\n\n\n";
    display(root);

}

Answer 1

This is a very C like approach and you are using C++ so take advantage of that fact.

1. Get rid of the #define and use nullptr keyword instead.

2. Name member variables something special such as m_ so Node *m_children[4];

3. Try use C++ data structures instead of arrays and char* so vector<Node*> children.

4. Make the Node struct into a class and write getters and setters to encapsulate the new vector structure you should use.

5. Encapsulate the void display(Node *root) function into a class such:

   class Tree
   {
       Tree(int depth);// create a tree with x depth
       etc...
       void display();
   public:
       Node* m_root;
   };
   

   You could create some functionality to able to initialise the tree with some custom data structure.

6. Add the following code in main into the tree class

   for (i=0;i<4;i++)
   {
       Node *temp=new Node;
       temp->value=values[i];
       root->child[i]=temp;
       for (int j=0;j<4;j++)
       {
           root->child[i]->child[j]=null;
       }
       std::cout<<"Root value "<<root->child[i]->value<<"\n\n ";
   }
   

PS. Sorry if the code doesn't work; I'm at work and have no way to check it!

Answer 2

This is correct enough.

You could improve it in a couple of ways,

• if you do new Node(), note the additional (), its members will be zero initialized, so you can skip the nulling of the children.
• you can add a constructor which initializes among other things the arrays to null, so that you don't need to remember to do it every time, Recommended for readability and future proof as commenters suggest?