leetcode/binary-tree-maximum-path-sum.py at main · atib92/leetcode · GitHub

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"""
Binary Tree Maximum Path Sum
Solved
Hard
Topics
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A path in a binary tree is a sequence of nodes where each pair of adjacent nodes in the sequence has an edge connecting them. A node can only appear in the sequence at most once. Note that the path does not need to pass through the root.

The path sum of a path is the sum of the node's values in the path.

Given the root of a binary tree, return the maximum path sum of any non-empty path.


Example 1:


Input: root = [1,2,3]
Output: 6
Explanation: The optimal path is 2 -> 1 -> 3 with a path sum of 2 + 1 + 3 = 6.
Example 2:


Input: root = [-10,9,20,null,null,15,7]
Output: 42
Explanation: The optimal path is 15 -> 20 -> 7 with a path sum of 15 + 20 + 7 = 42.


Constraints:

The number of nodes in the tree is in the range [1, 3 * 104].
-1000 <= Node.val <= 1000
"""
class Solution:
    def _maxPathSum(self, root):
        if root is None:
            return 0
        else:
            left = self._maxPathSum(root.left)
            right = self._maxPathSum(root.right)
            self.max_sum = max(self.max_sum, root.val+max(0, left) + max(0, right))
            return max(0,max(left, right)) + root.val
    def maxPathSum(self, root: Optional[TreeNode]) -> int:
         self.max_sum = float("-inf")
         self._maxPathSum(root)
         return self.max_sum