Java Program to Count the number of nodes in a binary tree

     Binary tree is a data structure which a root and nodes. Here, a root is like a parent. Nodes are like children. It has a structure of root, left child and right child.

Let us count the number of nodes in a binary tree. Binary tree has two nodes in all levels.

Program implementation:

• ·       Create a node with data and left child and right child.
• ·       Initialise the values.
• ·       Create a binary tree class. Declare a variable for root.
• ·       A function is defined to count the nodes.
• ·       Using a recursive function, count it.
• ·       Let us invoke the main() function, to initialise the objects.
• ·       Use the objects to call the function.
• ·       Print the number of nodes in the output screen.

Classes incuded:

Node: It defines the structureof node.

BinaryTreeEg : It defines the structure of binary tree.

Variables:

‘data’ , ‘value’, ‘c_left’,’c_right’

Functions:

‘countIt()’ – This function counts the number of nodes.

‘main()’ – It creates the objects and calls the function to get the output.

Program:

class Node {

    int data;

    Node c_left, c_right;

    Node(int value) {

        data = value;

       c_left = c_right = null;

    }

}

class BinaryTreeEg {

    Node root;

    // countIt method to count the nodes in the binary tree

    public int countIt(Node node) {

        if (node == null) {

            return 0;

        }

        // A recursive function to count the nodes

        return 1 + countIt(node.c_left) + countIt(node.c_right);

    }

    public static void main(String[] args) {

        BinaryTreeEg bt = new BinaryTreeEg();

        // Creating a sample binary tree

        bt.root = new Node(10);

        bt.root.c_left = new Node(20);

        bt.root.c_right = new Node(30);

        bt.root.c_left.c_left = new Node(40);

        bt.root.c_left.c_right = new Node(50);

        bt.root.c_right.c_left = new Node(60);

        bt.root.c_right.c_right = new Node(70);

        System.out.println("Number of nodes in the binary tree: " + bt.countIt(bt.root));

    }

}

Output:

Compile and run the program to get the output.

C:\raji\blog>javac BinaryTreeEg.java

C:\raji\blog>java BinaryTreeEg

Number of nodes in the binary tree: 7

That’s all. The java program to count the number of nodes in a binary tree was implemented successfully. Hope this code is useful to you. Happy coding!!