"apple"->NULL return "apple"->"apple"->NULL 

"green"->"green"->"blue"->"red"->"green"->NULL return "green"->"green"->"blue"->"blue"->"red"->"red"->"green"->"green"->NULL 

Create a function expand, which takes in a pointer to the head of the linked list, and returns a pointer to the head of a linked list in which all strings repeat following the rules described above.

Example:

The linked lists for this problem use the following class declaration:

class node { public: string data; node* next; }; 

Do this in C++.

Code in bold CANNOT be changed:

node* expand(node* head) { while(head != NULL) { head->data = head->data+head->next; head = head->next; } }