Given a binary tree, return the\u00a0bottom-up level order<\/i>\u00a0traversal of its nodes’ values. (ie, from left to right, level by level from leaf to root).<\/p>\n
For example: return its bottom-up level order traversal as:<\/p>\n Python<\/strong><\/p>\n
\nGiven binary tree\u00a0[3,9,20,null,null,15,7]<\/code>,<\/p>\n 3\r\n \/ \\\r\n 9 20\r\n \/ \\\r\n 15 7\r\n<\/pre>\n
[\r\n [15,7],\r\n [9,20],\r\n [3]\r\n]<\/pre>\n
\r\n# Definition for a binary tree node.\r\n# class TreeNode(object):\r\n# def __init__(self, x):\r\n# self.val = x\r\n# self.left = None\r\n# self.right = None\r\n\r\nclass Solution(object):\r\n def __init__(self):\r\n self.temp_result = dict()\r\n self.result = list()\r\n self.level = 0\r\n def levelOrderBottom(self, root):\r\n """\r\n :type root: TreeNode\r\n :rtype: List[List[int]]\r\n """\r\n if root:\r\n self.return_node([root])\r\n for i in range(0,len(self.temp_result)):\r\n self.result.append(self.temp_result[i])\r\n\r\n return self.result[::-1]\r\n\r\n else:\r\n return []\r\n\r\n\r\n def return_node(self, root_list):\r\n if root_list:\r\n temp_list = []\r\n for i in root_list:\r\n temp_list.append(i.val)\r\n self.temp_result[self.level] = temp_list\r\n self.level += 1\r\n new_root_list = list()\r\n for i in root_list:\r\n if i:\r\n if i.left:\r\n new_root_list.append(i.left)\r\n if i.right:\r\n new_root_list.append(i.right)\r\n print(new_root_list)\r\n return self.return_node(new_root_list)\r\n return\r\n\r\n \r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"