102. Binary Tree Level Order Traversal

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def levelOrder(self, root: TreeNode) -> List[List[int]]:
        result = []
        if not root:
            current = []
        else:
            current = [root]
        
        while current != []:
            result.append([node.val for node in current])
            new = []
            for node in current:
                if node.left:
                    new.append(node.left)
                if node.right:
                    new.append(node.right)
            current = new
            
        return result