# Time:  O(n)
# Space: O(n)

# Given a binary tree, return the bottom-up level order traversal
# of its nodes' values.
#  (ie, from left to right, level by level from leaf to root).
#
# For example:
# Given binary tree {3,9,20,#,#,15,7},
#     3
#    / \
#   9  20
#     /  \
#    15   7
# return its bottom-up level order traversal as:
# [
#   [15,7],
#   [9,20],
#   [3]
# ]

import collections


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


class Solution(object):
    def levelOrderBottom(self, root):
        """
        :type root: TreeNode
        :rtype: List[List[int]]
        """
        ans = []
        if not root: return ans

        q = collections.deque([root])
        while q:
            level, sz = [], len(q)
            for _ in range(sz):
                node = q.popleft()
                level.append(node.val)
                if node.left:
                    q.append(node.left)
                if node.right:
                    q.append(node.right)
            ans.append(level)
        return ans[::-1]

    def levelOrderBottom_kamyu(self, root):
        if root is None:
            return []

        result, current = [], [root]
        while current:
            next_level, vals = [], []
            for node in current:
                vals.append(node.val)
                if node.left:
                    next_level.append(node.left)
                if node.right:
                    next_level.append(node.right)
            current = next_level
            result.append(vals)

        return result[::-1]

# Time:  O(n)
# Space: O(n)

# Given a binary tree, return the bottom-up level order traversal
# of its nodes' values.
#  (ie, from left to right, level by level from leaf to root).
#
# For example:
# Given binary tree {3,9,20,#,#,15,7},
#     3
#    / \
#   9  20
#     /  \
#    15   7
# return its bottom-up level order traversal as:
# [
#   [15,7],
#   [9,20],
#   [3]
# ]

import collections


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


class Solution(object):
    def levelOrderBottom(self, root):
        """
        :type root: TreeNode
        :rtype: List[List[int]]
        """
        ans = []
        if not root: return ans

        q = collections.deque([root])
        while q:
            level, sz = [], len(q)
            for _ in range(sz):
                node = q.popleft()
                level.append(node.val)
                if node.left:
                    q.append(node.left)
                if node.right:
                    q.append(node.right)
            ans.append(level)
        return ans[::-1]

    def levelOrderBottom_kamyu(self, root):
        if root is None:
            return []

        result, current = [], [root]
        while current:
            next_level, vals = [], []
            for node in current:
                vals.append(node.val)
                if node.left:
                    next_level.append(node.left)
                if node.right:
                    next_level.append(node.right)
            current = next_level
            result.append(vals)

        return result[::-1]

# Time:  O(n) # Space: O(n) # Given a binary tree, return the bottom-up level order traversal # of its nodes' values. #  (ie, from left to right, level by level from leaf to root). # # For example: # Given binary tree {3,9,20,#,#,15,7}, #     3 #    / \ #   9  20 #     /  \ #    15   7 # return its bottom-up level order traversal as: # [ #   [15,7], #   [9,20], #   [3] # ] # Definition for a  binary tree node :type root: TreeNode         :rtype: List[List[int]]