Problem Populating Next Right Pointers in Each Node II

Problem Description:

Follow up for problem "Populating Next Right Pointers in Each Node".

What if the given tree could be any binary tree? Would your previous solution still work?

Note:

• You may only use constant extra space.

 

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) {
        if (root == null) {
            return;
        }

        TreeLinkNode cur = root.next;
        TreeLinkNode p  = null;
        while (cur != null) {
            if (cur.left != null) {
                p = cur.left;
                break;
            }
            if (cur.right != null) {
                p = cur.right;
                break;
            }
            cur = cur.next;
        }

        if (root.right != null) {
            root.right.next = p;
        }
        if (root.left != null) {
            root.left.next = root.right != null ? root.right : p;
        }

        connect(root.right);
        connect(root.left);
    }