LeetCode Populating Next Right Pointers in Each Node

原题链接在这里：https://leetcode.com/problems/populating-next-right-pointers-in-each-node/

递归调用，如果root.next不为null, root.right.next借助于root.next.left, 然后root.left.next指向root.right.

若是算上递归，Space O(logn).

AC Java:

/**
 * 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;
        }
        if(root.right != null && root.next != null){
            root.right.next = root.next.left;
        } 
        if(root.left!=null){
            root.left.next = root.right;
        }
        connect(root.right);
        connect(root.left);
    }
}