Populating Next Right Pointers in Each Node

main.py

class Solution:
    def connect(self, node):
        if not node:
            return None
        # For every node...
        # 1. We will connect it's left child to it's right child. (If it has children).
        if node.left and node.right:
            node.left.next = node.right
            # 2. Connect it's right child to the current node's next's left child. (If it has a next node).
            if node.next:
                node.right.next = node.next.left
        self.connect(node.left)
        self.connect(node.right)
        return node