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Leetcode: Linked List Cycle

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

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

分析:如果一个linked list中有环,那么在用一个快指针和一个慢指针遍历该linked list时,这两个指针必会相交。代码如下:

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

 

Leetcode: Linked List Cycle