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binary-tree-maximum-path-sum.py
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binary-tree-maximum-path-sum.py
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# Time: O(n)
# Space: O(h), h is height of binary tree
#
# Given a binary tree, find the maximum path sum.
#
# The path may start and end at any node in the tree.
#
# For example:
# Given the below binary tree,
#
# 1
# / \
# 2 3
# Return 6.
#
# 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")
# @param root, a tree node
# @return an integer
def maxPathSum(self, root):
self.maxPathSumRecu(root)
return self.maxSum
def maxPathSumRecu(self, root):
if root is None:
return 0
left = max(0, self.maxPathSumRecu(root.left))
right = max(0, self.maxPathSumRecu(root.right))
self.maxSum = max(self.maxSum, root.val + left + right)
return root.val + max(left, right)
if __name__ == "__main__":
root = TreeNode(1)
root.left = TreeNode(2)
root.right = TreeNode(3)
result = Solution().maxPathSum(root)
print result