Create a function cycle_length, which takes in a pointer to the head of the linked list, and, if there is a cycle in the linked list, returns the length of the cycle. If there is no cycle, your function should return -1.

class node { public: node* next; }; 

Example:

0->1->2->3->NULL return -1 

0->1->2->3->4->5->6->7->8->9->4 return 6 

Do this in C++. Code in bold CANNOT be changed:

int cycle_length(node* head) { // fill in code here

}