# Populating Next Right Pointers in Each Node II

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
``````

https://leetcode.com/problems/populating-next-right-pointers-in-each-node-ii/

Solution:

I: with O(lgN) space:

level order traversal with a queue

II: with O(1) space:

``````/**
* Definition for binary tree with next pointer.
*     int val;
*     TreeLinkNode(int x) { val = x; }
* }
*/
public class Solution {
// Note: The Solution object is instantiated only once and is reused by each test case.
if (root == null) {
return;
}

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

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

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

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