Populating Next Right Pointers in Each Node

Medium(https://leetcode.com/problems/populating-next-right-pointers-in-each-node/submissions/)

You are given a perfect binary tree where all leaves are on the same level, and every parent has two children. The binary tree has the following definition:

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.