Implement a circular linked list

A circular linked list is the same as a singular linked list except that there last node points to the first node.

Here is the specification of my CiLinkedList.

• CiLinkedList(), Create an empty CiLinkedList.
• CiLinkedList(const CiLinkedList& list), Create a CiLinkedList from another CiLinkedList list.
• CiLinkedList(const T& value), Create a CiLinkedList whose first element is value.
• CiLinkedList(const T values[], size_t size), Create a CiLinkedList from an array values of size size.
• const CiLinkedList& operator=(const CiLinkedList& list), Support CiLinkedList assignment.
• ~CiLinkedList(), Free all the space requested by the CiLinkedList.
• std::ostream& operator<<(std::ostream&, const CiLinkedList<T>&);, Output the CiLinkedList in the form [a, b, c …].
• const T& operator[](size_t index), Access the element of the CiLinkedList, but it’s not random accessible.
• size_t size(), Return the size of the CiLinkedList.
• rm_dup(), Remove duplicate elements int the CiLinkedList.

Here is the code.