二叉树的层序遍历

from collections import deque
class TreeNode:
    def __init__(____):
        self.val = val
        self.left = left
        self.right = right

def solve():
    def levelOrder(____):
        if not root:
            return []
        result = []
        queue = deque(____)
        while queue:
            level = []
            for _ in range(len(____)):
                node = queue.popleft()
                level.append(____)
                if node.left:
                    queue.append(____)
                if node.right:
                    queue.append(____)
            result.append(____)
        return result
    root = TreeNode(____, TreeNode(____), TreeNode(____, TreeNode(____), TreeNode(____)))
    print(levelOrder(____))