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BinaryTreeMaximumPathSum.java

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/*

Author: Andy, nkuwjg@gmail.com

Date: Jan 28, 2015

Problem: Binary Tree Maximum Path Sum

Difficulty: Easy

Source: https://oj.leetcode.com/problems/binary-tree-maximum-path-sum/

Notes:

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.

Solution: Recursion...

*/

/**

* Definition for binary tree

* public class TreeNode {

* int val;

* TreeNode left;

* TreeNode right;

* TreeNode(int x) { val = x; }

* }

*/

public class Solution {

public int maxPathSum(TreeNode root) {

int[] res = new int[1];

res[0] = Integer.MIN_VALUE;

maxPathSumRe(root, res);

return res[0];

}

int maxPathSumRe(TreeNode root, int[] res) {

if (root == null) return 0;

int left = maxPathSumRe(root.left, res);

int right = maxPathSumRe(root.right, res);

res[0] = Math.max(res[0], root.val + Math.max(left, 0) + Math.max(right, 0));

return Math.max(root.val, root.val + Math.max(left, right));

}

}