public static int findMaxUniqueNodesInPath(TreeNode root){
        //gate keep
        if(root == null)
            return 0;

        //create seen hashMap
        HashMap<Integer, Integer> seenMap = new HashMap<Integer,Integer>();

        return findMaxUniqueUtil(root, seenMap);
    }

    public static int findMaxUniqueUtil(TreeNode root, HashMap<Integer,Integer> seemMap){
        if(root == null)
            return seemMap.size();

        //store into hashMap
        if(seemMap.containsKey(root.val)) {
            int size = seemMap.size();
            seemMap.clear();
            return size;
        }
//            seemMap.put(root.val, seemMap.get(root.val)+1);

        else
            seemMap.put(root.val,1);


        int maxLength = Math.max(findMaxUniqueUtil(root.left, seemMap), findMaxUniqueUtil(root.right,seemMap));

//        if(seemMap.containsKey(root.val))
//            seemMap.put(root.val,seemMap.get(root.val) -1);

//        if(seemMap.get(root.val) == 0) {
//            seemMap.remove(root.val);
//            return maxLength;
//        }
        return maxLength;

    }

    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(3);
        root.left.left = new TreeNode(2);
        root.right.left = new TreeNode(3);
        root.right.right = new TreeNode(1);
        root.right.right.left = new TreeNode(5);
        root.right.right.right = new TreeNode(6);
        System.out.println(findMaxUniqueNodesInPath(root));

        TreeNode root2 = new TreeNode(1);
        root2.left =  new TreeNode(2);
        root2.left.left = new TreeNode(4);
        root2.left.right = new TreeNode(5);
        root2.right = new TreeNode(3);
        root2.right.left = new TreeNode(6);
        root2.right.right = new TreeNode(3);
        root2.right.left.right = new TreeNode(8);
        root2.right.right.right = new TreeNode(9);
        System.out.println(findMaxUniqueNodesInPath(root2));

        TreeNode root3 = new TreeNode(1);
        root3.right = new TreeNode(2);
        root3.right.left = new TreeNode(1);
        root3.right.right = new TreeNode(1);
        root3.right.right.left = new TreeNode(4);
        System.out.println(findMaxUniqueNodesInPath(root3));
        
    }