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

Example

Given -21->10->4->5, tail connects to node index 1, return true

Challenge

Follow up:

Can you solve it without using extra space?

 

LeetCode上的原题，请参见我之前的博客。

 

class Solution {public:    /**     * @param head: The first node of linked list.     * @return: True if it has a cycle, or false     */    bool hasCycle(ListNode *head) {        if (!head) return false;        ListNode *slow = head, *fast = head;        while (fast && fast->next) {            slow = slow->next;            fast = fast->next->next;            if (slow == fast) return true;        }        return false;    }};