Double a binary tree

Double.java

// Java program to convert binary tree to double tree
// http://www.geeksforgeeks.org/double-tree/

class Node 
{
	int data;
	Node left, right;

	Node(int item) 
	{
		data = item;
		left = right = null;
	}
}

class BinaryTree 
{
	Node root;

	/* Function to convert a tree to double tree */
	void doubleTree(Node node) 
	{
		 Node oldleft;

		 if (node == null)
			return;

		 // create a duplicate node and insert it middle 
     // call recurvisley using the old node left
    
		
		 /* duplicate this node to its left */
		 oldleft = node.left;
		 node.left = new Node(node.data);
		 node.left.left = oldleft;
		
		 // note - we are calling left.left. 
     doubleTree(node.left.left);
		 doubleTree(node.right);
	}

	/* Given a binary tree, print its nodes in inorder*/
	void printInorder(Node node) 
	{
		if (node == null)
			return;
		printInorder(node.left);
		System.out.print(node.data + " ");
		printInorder(node.right);
	}

	/* Driver program to test the above functions */
	public static void main(String args[]) 
	{
		/* Constructed binary tree is
			1
			/ \
		2	 3
		/ \
		4 5
		*/
		BinaryTree tree = new BinaryTree();
		tree.root = new Node(1);
		tree.root.left = new Node(2);
		tree.root.right = new Node(3);
		tree.root.left.left = new Node(4);
		tree.root.left.right = new Node(5);
        
        tree.root.right = new Node(7);


		System.out.println("Original tree is : ");
		tree.printInorder(tree.root);
		tree.doubleTree(tree.root);
		System.out.println("");
		System.out.println("Inorder traversal of double tree is : ");
		tree.printInorder(tree.root);
	}
}

// This code has been contributed by Mayank Jaiswal(mayank_24)