Linked List Cycle

 1 class Solution {
 2 public:
 3     bool hasCycle(ListNode *head) {
 4         ListNode* slow = head;
 5         ListNode* fast = head;
 6         while (fast && fast->next){
 7             fast = fast->next->next;
 8             slow = slow->next;
 9             if (slow == fast)
10                 return true;
11         }
12         return false;
13     }
14 };