116. Populating Next Right Pointers in Each Node

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

JavaScript

/**
 * // Definition for a Node.
 * function Node(val,left,right,next) {
 *    this.val = val;
 *    this.left = left;
 *    this.right = right;
 *    this.next = next;
 * };
 */
/**
 * @param {Node} root
 * @return {Node}
 */
function connect(root) {
  if (!root) {
    return root
  }
  if (root.left) {
    root.left.next = root.right
  }
  if (root.right && root.next) {
    root.right.next = root.next.left
  }
  connect(root.left)
  connect(root.right)
  return root
}

Python

"""
# Definition for a Node.
class Node(object):
    def __init__(self, val, left, right, next):
        self.val = val
        self.left = left
        self.right = right
        self.next = next
"""


class Solution(object):

    def connect(self, root):
        """
        :type root: Node
        :rtype: Node
        """
        if not root:
            return root
        if root.left:
            root.left.next = root.right
        if root.right and root.next:
            root.right.next = root.next.left
        self.connect(root.left)
        self.connect(root.right)
        return root

Go

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 *     Next *TreeNode
 * }
 */
func connect(root *TreeNode) *TreeNode {
	if root == nil {
		return root
	}
	if root.Left != nil {
		root.Left.Next = root.Right
	}
	if root.Right != nil && root.Next != nil {
		root.Right.Next = root.Next.Left
	}
	connect(root.Left)
	connect(root.Right)
	return root
}