LeetCode力扣之116. Populating Next Right Pointers in Each Node

Given a binary tree struct TreeLinkNode {
TreeLinkNode *left;
TreeLinkNode *right;
TreeLinkNode *next;
}
Populate each next pointer to point to its next right node. If there is no next right node, the next pointer should be set to 

NULL

.Initially, all next pointers are set to 

NULL

.Note:You may only use constant extra space.
You may assume that it is a perfect binary tree (ie, all leaves are at the same level, and every parent has two children).
For example,
Given the following perfect binary tree,
1
/ \
2 3
/ \ / \
4 5 6 7
After calling your function, the tree should look like:
1 -> NULL
/ \
2 -> 3 -> NULL
/ \ / \
4->5->6->7 -> NULL
package leetCode;

/**
* Created by lxw, liwei4939@126.com on 2018/3/25.
*/

class TreeLinkedNode{
int val;
TreeLinkedNode left, right, next;
TreeLinkedNode(int x){
this.val = x;
}
}
public class L116_PopulatingNextRight {

public void connect(TreeLinkedNode root){
if (root == null){
return;
}
if (root.left != null){
root.left.next = root.right;
}

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

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