[LeetCode]124 Binary Tree Maximum Path Sum

/**
* 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) {

if (root == null)
return 0;

Result result = new Result();
result.value = Integer.MIN_VALUE;
visit(root, result);
return result.value;
}

Values visit(TreeNode node, Result result)
{
int full = 0;
int sub = 0;

if (node.left == null && node.right == null)
{
sub = node.val;
full = sub;
}
else if (node.left != null && node.right == null)
{
Values leftvalues = visit(node.left, result);

sub = max(node.val, node.val + leftvalues.sub);
full = sub;
}
else if (node.left == null && node.right != null)
{
Values rightvalues = visit(node.right, result);

sub = max(node.val, node.val + rightvalues.sub);
full = sub;
}
else
{
// If curren node has both left and right
//
// the maxpath passing this node would be
// max( node.val,   this node only
//      node.val + left.sub     this node with left sub tree
//      node.val + right.sub    this node with right sub tree
//      node.val + left.sub + right.sub     this path from its left subtree to right subtree
//
// However,
// the maxpath when current node is subtree
// it cannot be
// (node.val + left.sub + right.sub)
Values leftvalues = visit(node.left, result);
Values rightvalues = visit(node.right, result);
sub = max(node.val,
node.val + leftvalues.sub,
node.val + rightvalues.sub);
full = max(sub,
node.val + leftvalues.sub + rightvalues.sub);
}

result.value = max(result.value, full);
return new Values(full, sub);
}

private int max(int...ints)
{
int r = Integer.MIN_VALUE;
for (int i : ints)
r = Math.max(r, i);
return r;
}

private static class Values
{
// MathPath when passing this node.
private int full;

// MathPath when using this node as a sub tree.
// NOTE
// It is different from full that
// current node must be endpoint.
private int sub;

Values(int full, int sub)
{
this.full = full;
this.sub = sub;
}
}

private static class Result
{
private int value;
}
}