二叉树中的最大路径和

private class ResultType {        // singlePath: 从root往下走到任意点的最大路径，这条路径可以不包含任何点        // maxPath: 从树中任意到任意点的最大路径，这条路径至少包含一个点        int signlePath, maxPath;         ResultType(int signlePath, int maxPath) {            this.signlePath = signlePath;            this.maxPath = maxPath;        }    }     public int maxPathSum(TreeNode root) {        // write your code here        return helper(root).maxPath;           }    public ResultType helper(TreeNode root){        if (root == null){            return new ResultType(0, Integer.MIN_VALUE);        }        ResultType left = helper(root.left);        ResultType right = helper(root.right);        int signlePath = Math.max(left.signlePath, right.signlePath) + root.val;        signlePath = Math.max(signlePath, 0);        int maxPath = Math.max(left.maxPath, right.maxPath);        /*maxPath = Math.max(maxPath, left.siglePath + right.siglePath + root.val);*/        maxPath = Math.max(maxPath, left.signlePath + right.signlePath + root.val);        return new ResultType(signlePath, maxPath);    }}