141. 环形链表 - 力扣（LeetCode）

class Solution {
public:
    bool hasCycle(ListNode *head) {
        ListNode* slow = head;
        ListNode* fast = head;

        while(fast != NULL &&fast->next != NULL)
        {

            fast = fast->next->next;
            slow = slow->next;
            if(fast == slow)
            {
                return true;
            }

        }
        return false;
    }
};