107. 二叉树的层次遍历 II

https://leetcode-cn.com/problems/binary-tree-level-order-traversal-ii/description/

解法一：

层序遍历，然后结果倒序

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
import queue
class Solution:
    def levelOrderBottom(self, root: TreeNode) -> List[List[int]]:
        res = []
        if not root:
            return res

        q = queue.Queue()
        q.put(root)
        while not q.empty():
            count = q.qsize()
            data = []
            for _ in range(count):
                node = q.get()
                data.append(node.val)
                if node.left:
                    q.put(node.left)
                if node.right:
                    q.put(node.right)
            res.append(data)
        res = res[::-1]
        return res