[LeedCode OJ] #141 Linked List Cycle,

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Author: User

[LeedCode OJ] #141 Linked List Cycle,

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Link: https://leetcode.com/problems/linked-list-cycle/


Give a linked list and determine whether the linked list has loops.


Set the speed pointer. The speed pointer takes two steps at a time, and the slow pointer takes one step at a time. If the fast pointer reaches NULL, it indicates that there is no loop. Once the fast pointer is equal to the slow pointer, it indicates that there is a loop.

/** * Definition for singly-linked list. * struct ListNode { *     int val; *     ListNode *next; *     ListNode(int x) : val(x), next(NULL) {} * }; */class Solution{public:    bool hasCycle(ListNode *head)    {        if(head==NULL)            return false;        ListNode *fast,*slow;        fast = slow = head->next;        while(fast!=NULL&&fast->next!=NULL)        {            fast = fast->next->next;            slow = slow->next;            if(fast==slow)                return true;        }        return false;    }};

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