124. Binary Tree Maximum Path Sum

class Solution:
    def maxPathSum(self, root: TreeNode) -> int:
        self.max_path_sum = float('-inf')
        self.pathsum(root)
        return self.max_path_sum
    
    def pathsum(self,node):
        if not node:
            return 0
        left = max(0,self.pathsum(node.left))
        right = max(0,self.pathsum(node.right))
        self.max_path_sum = max(self.max_path_sum, left + right + node.val)
        return max(left,right) + node.val