Leetcode -- 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 shoshould be setNULL.

Initially, all next pointers are setNULL.

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 shoshould look like:

         1 -> NULL       /        2 -> 3 -> NULL     / \  /     4->5->6->7 -> NULL

Original question link: https://oj.leetcode.com/problems/populating-next-right-pointers-in-each-node/

Question: Given a binary tree (assuming a Complete Binary Tree), point the next pointer of each node to its right node.

Thought: First of all, we thought of a sequence traversal tree, adding a pointer to the right node while traversing.

Another simple method is recursion, which is simple and intuitive.

public void connect(TreeLinkNode root) {if (root == null)return;if (root.left != null)root.left.next = root.right;if (root.right != null)root.right.next = root.next == null ? null : root.next.left;connect(root.left);connect(root.right);}// Definition for binary tree with next pointer.public class TreeLinkNode {int val;TreeLinkNode left, right, next;TreeLinkNode(int x) {val = x;}}