递归创建一棵树

class TreeNode:
    def __init__(self, val=0, children=None):
        self.val = val
        self.children = children if children is not None else []

def create_tree(tree_data):
    if not tree_data:
        return None
    
    root = TreeNode(tree_data[0])
    children = tree_data[1] if len(tree_data) > 1 else []
    
    for child in children:
        root.children.append(create_tree(child))
    
    return root

tree_data = [
    1,
    [
        [2, [4]],
        [3, [5, [6]]]
    ]
]

root = create_tree(tree_data)