【leetcode】1302. Deepest Leaves Sum

题目如下：

Given a binary tree, return the sum of values of its deepest leaves.

Example 1:

Input: root = [1,2,3,4,5,null,6,7,null,null,null,null,8]
Output: 15

Constraints:

• The number of nodes in the tree is between 1 and 10^4.
• The value of nodes is between 1 and 100.

解题思路：我的方法是做两次遍历，第一次求树的最大深度，第二次求和。

代码如下：

# 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):
    level = 0
    leavesSum = 0
    def getMaxLevel(self,node,level):
        self.level = max(self.level,level)
        if node == None:
            return
        if node.left != None:
            self.getMaxLevel(node.left,level + 1)
        if node.right != None:
            self.getMaxLevel(node.right,level + 1)
    def calc(self,node,level):
        if level == self.level:
            self.leavesSum += node.val
        if node == None:
            return
        if node.left != None:
            self.calc(node.left,level + 1)
        if node.right != None:
            self.calc(node.right,level + 1)


    def deepestLeavesSum(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        self.leavesSum = 0
        self.level = 0
        self.getMaxLevel(root,0)
        self.calc(root,0)
        return self.leavesSum