429. N叉树的层序遍历

class Solution(object):
    def levelOrder(self, root):
        """
        :type root: Node
        :rtype: List[List[int]]
        """
        if not root:
            return []
        ans = []
        self.dfs(1, root, ans)
        return ans

    def dfs(self, level, root, ans):
        if len(ans) < level:
            ans.append([])
        ans[level].append(root.val)
        # 递归遍历子树
        for tNode in root.children:
            self.dfs(level + 1, tNode, ans)
        return ans