Leetcode -- linked list cycle -- determine whether the linked list has a ring

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

Follow up:
Can you solve it without using extra space?

This topic uses the speed pointer to focus on how the code is implemented in a concise and easy way.

Here, we use a fast pointer to determine whether the linked list is null. If there is no null, we can continue to see if it can meet the slow pointer.

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

Leetcode -- linked list cycle -- determine whether the linked list has a ring