给出一棵二叉树，寻找一条路径使其路径和最大，路径可以在任一节点中开始和结束（路径和为两个节点之间所在路径上的节点权值之和）
样例
给出一棵二叉树：
1
/ \
2 3
返回 6
代码:
/**
* Definition of TreeNode:
* public class TreeNode {
* public int val;
* public TreeNode left, right;
* public TreeNode(int val) {
* this.val = val;
* this.left = this.right = null;
* }
* }
*/
public class Solution {
/**
* @param root: The root of binary tree.
* @return: An integer.
*/
int max = Integer.MIN_VALUE;
public int maxPathSum(TreeNode root) {
if(null == root)
{
return 0;
}
subMaxPathSum(root);
return max;
}
public int subMaxPathSum(TreeNode node)
{
if(null == node)
{
return 0;
}
int leftMax = subMaxPathSum(node.left);
int rightMax = subMaxPathSum(node.right);
int subMax = Math.max(Math.max(Math.max(leftMax + node.val, rightMax + node.val), node.val),leftMax + rightMax + node.val);
if(max < subMax)
{
max = subMax;
}
return Math.max(Math.max(leftMax + node.val, rightMax + node.val), node.val);
}
}
