public static void main(String[] args) {
        TreeNode root = new TreeNode(1);
        root.left = new TreeNode(2);
        root.right = new TreeNode(3);
        root.left.left = new TreeNode(4);
        root.left.right = new TreeNode(5);
        root.right.left = new TreeNode(6);
        root.right.right = new TreeNode(7);
        BinaryTreePath p = new BinaryTreePath();
        p.getPath(root);
        for (ArrayList<Integer> arr : p.ans) {
            for (int i : arr) {
                System.out.print(i + " ");
            }
            System.out.println();
        }
    }