static void Main(string[] args)
{
TreeNode root = new TreeNode(9);
TreeNode n1 = new TreeNode(6);
TreeNode n2 = new TreeNode(-3);
TreeNode n3 = new TreeNode(-6);
TreeNode n4 = new TreeNode(2);
TreeNode n5 = new TreeNode(2);
TreeNode n6 = new TreeNode(-6);
TreeNode n7 = new TreeNode(-6);
TreeNode n8 = new TreeNode(-6);
root.left = n1;
root.right = n2;
n2.left = n3;
n2.right = n4;
n4.left = n5;
n5.left = n6;
n5.right = n7;
n6.left = n8;
Program p = new Program();
int res = p.MaxPathSum(root);
Console.WriteLine(res);
Console.ReadKey();
}
public int CalcPathSum(TreeNode node)
{
int pathSum = node.val;
if (max < pathSum) max = pathSum;
int pathLeft = 0, pathRight = 0;
if (node.left != null)
{
pathLeft = CalcPathSum(node.left);
if (pathLeft > 0)
{
pathSum += pathLeft;
if (max < pathSum) max = pathSum;
}
}
if (node.right != null)
{
pathRight = CalcPathSum(node.right);
if (pathRight > 0)
{
pathSum += pathRight;
if (max < pathSum) max = pathSum;
}
}
// max between left path and right path, should not include both
int res = node.val + (pathLeft > pathRight ? pathLeft : pathRight);
return res>0?res:0;
}
public int MaxPathSum(TreeNode root)
{
if (root == null) return 0;
max = int.MinValue;
CalcPathSum(root);
return max;
}