LC 0117 [M] Populating Next Right Pointers in Each Node II - ALawliet/algorithms GitHub Wiki

"""
# Definition for a Node.
class Node:
    def __init__(self, val: int = 0, left: 'Node' = None, right: 'Node' = None, next: 'Node' = None):
        self.val = val
        self.left = left
        self.right = right
        self.next = next
"""

class Solution:
    def connect(self, root: 'Node') -> 'Node':
        if not root:
            return root
        
        Q = deque([root])
        
        while Q:
            prev = None
            
            for _ in range(len(Q)):
                node = Q.popleft()
                
                if prev:
                    prev.next = node
                prev = node
                
                if node.left:
                    Q.append(node.left)
                if node.right:
                    Q.append(node.right)
                    
        return root