Populating Next Right Pointers in Each Node in a Binary Tree

Populating Next Right Pointers in Each Node if the given tree is a binary tree? 

For example,

Given the following binary tree,

         1
       /  \
      2    3
     / \    \
    4   5    7

After calling your function, the tree should look like:

         1 -> NULL
       /  \
      2 -> 3 -> NULL
     / \    \
    4-> 5 -> 7 -> NULL

Solution:

 public void connect(TreeLinkNode root) {

        Queue<TreeLinkNode> queue = new LinkedList<TreeLinkNode>();

        

        if(root==null)

            return;

        queue.add(root);

        // add null to remember level

        queue.add(null);

        while(!queue.isEmpty()) {

            TreeLinkNode temp = queue.poll();

            if(temp!=null) {

                temp.next = queue.peek();

                if(temp.left!=null) {

                    queue.add(temp.left);

                }

                if(temp.right!=null) {

                    queue.add(temp.right);

                }

            }

            // if queue is not empty, push NULL to mark nodes at this level are visited

            else if(!queue.isEmpty()) {

                queue.add(null);

            }

            

        }

    }