리트코드 141. Linked List Cycle // 플로이드 사이클 검사

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

풀이1

/**
 * Definition for singly-linked list.
 * class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public boolean hasCycle(ListNode head) {
        HashMap<ListNode,Boolean> m = new HashMap<>();

        while(head!=null){
            if(m.containsKey(head)){
                return true;
            }
            else{
                m.put(head,true);
            }
            head=head.next;
        }
        return false;
    }
}

풀이2 (플로이드 사이클)

public class Solution {
    public boolean hasCycle(ListNode head) {
        ListNode rabbit = head;
        ListNode tutle = head;
        while(rabbit!=null && rabbit.next!=null){
            tutle = tutle.next;
            rabbit = rabbit.next.next;
            if(tutle==rabbit){
                return true;
            }
        }
        return false;
    }
}