leetcode-141. Linked List Cycle

leetcode-141. Linked List Cycle

Given a linked list, determine if it has a cycle in it.

class Solution {
public:
    bool hasCycle(ListNode *head) {
       // if(!head || !head->next || !head -> next -> next) return false;
        ListNode* fast = head;
        ListNode* slow = head;
        while(fast && fast->next){
            fast = fast->next->next;
            slow = slow->next;
            if(fast == slow)
                return true;
        }
        return false;
    }
};