Serialize and deserialize BST

public class Codec {

    // Encodes a tree to a single string.
    public String serialize(TreeNode root) {
       if(root==null) return "#/";
 
        return root.val+"/"+serialize(root.left)+serialize(root.right);
    }

    // Decodes your encoded data to tree.
    public TreeNode deserialize(String data) {
        if(data.equals("#")) return null;
        int[] t={0};
        String[] arr=data.split("/");
        return helper(arr, t);
    }
    
    TreeNode helper(String[] arr, int[] t){
        if(arr[t[0]].equals("#")) return null;
        TreeNode root=new TreeNode(Integer.parseInt(arr[t[0]]));
        t[0]=t[0]+1;
        root.left=helper(arr, t);
        t[0]=t[0]+1;
        root.right=helper(arr, t);
        return root;
    }
}

// Your Codec object will be instantiated and called as such:
// Codec ser = new Codec();
// Codec deser = new Codec();
// String tree = ser.serialize(root);
// TreeNode ans = deser.deserialize(tree);
// return ans;
#Status: encountered such question for first time, took a long time