Write a piece of code that counts the number of duplicate elements in a linked list.

That is$,$ the number of elements whose values are repeated at an earlier index in the list. Assume that all duplicates in the list occur consecutively. For example, the list $[1,1,3,5,5,5,5,7,7,11]$ contains five duplicates: one duplicate of element value $1,$ three duplicates of element value $5,$ and one duplicate of element value $7.$

You must answer this question using an iterator $($note that using a foreach loop isn't sufficient $-$ you must create an iterator object and use that to solve this problem$)$