Populating next right pointers in each node II

Follow up for problem"Populating next right pointers in each node".

What if the given tree cocould be any binary tree? Wocould 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 shoshould look like:

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

Answer

/** * Definition for binary tree with next pointer. * public class TreeLinkNode { *     int val; *     TreeLinkNode left, right, next; *     TreeLinkNode(int x) { val = x; } * } */public class Solution {    public void connect(TreeLinkNode root) {        if(root==null)        {            return ;        }        TreeLinkNode firstUpper=root;        TreeLinkNode pUpper;        TreeLinkNode firstBelow=null;        TreeLinkNode pBelow=null;        while(firstUpper!=null)        {            pUpper=firstUpper;            while(pUpper!=null)            {                if(pUpper.left!=null)                {                    if(firstBelow==null)                    {                        firstBelow=pUpper.left;                        pBelow=firstBelow;                    }                    else                    {                        pBelow.next=pUpper.left;                        pBelow=pBelow.next;                    }                }                if(pUpper.right!=null)                {                    if(firstBelow==null)                    {                        firstBelow=pUpper.right;                        pBelow=firstBelow;                    }                    else                    {                        pBelow.next=pUpper.right;                        pBelow=pBelow.next;                    }                }                pUpper=pUpper.next;            }            firstUpper=firstBelow;            firstBelow=null;        }    }}

Populating next right pointers in each node II