Binary Tree Maximum Path Sum

Given a non-empty binary tree, find the maximum path sum. For this problem, a path is defined as any sequence of nodes from some starting node to any node in the tree along the parent-child connections. The path must contain at least one node and does not need to go through the root. Tags: Tree

Try It!

Discussion

Video

Solution

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def maxPathSum(self, root: TreeNode) -> int:
        self.res = float('-inf')
        self.helper(root)
        return self.res
    
    def helper(self, root):
        if not root:
            return 0
        left = self.helper(root.left)
        right = self.helper(root.right)
        if root.val + left + right > self.res:
            self.res = root.val + left + right

        pos_max_path = root.val + max(left, right)
        if pos_max_path > 0:
            return pos_max_path
        else:
            return 0