leetcode 563 二叉树坡度

这题用二叉树中序遍历想到了，坡度扔一个列表里面最后求和也想到了，没想到的是返回值是啥，很接近.......

# 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 findTilt(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        self.tiles = []
        self.getNodeTilt(root)
        return sum(self.tiles)

    def getNodeTilt(self, node):
        if not node:
            return 0
        lSum = self.getNodeTilt(node.left)
        rSum = self.getNodeTilt(node.right)
        self.tiles.append(abs(lSum - rSum))
        return node.val + lSum + rSum