124. 二叉树中的最大路径和

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

class Solution:
    maxSum = float("-inf")
    def maxPathSum(self, root: TreeNode) -> int:
        def my(node):
            if node==None:
                return 0
            # 计算当前节点的左右子树的和
            left=max(my(node.left),0)
            right=max(my(node.right),0)
            # 算出当前节点的最大和
            self.maxSum=max(node.val+left+right,self.maxSum)
            return node.val+max(left,right)

        my(root)
        return self.maxSum
# 参考官方题解思路