题解 | #判断链表中是否有环#

import java.util.*;
/**
 * 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) {
        ArrayList<ListNode> tempData = new ArrayList<>();
        ListNode tempNode = head;
        while (tempNode != null) {
            if (!tempData.isEmpty()) {
                for (ListNode i : tempData) {
                    if (i.equals(tempNode)) {
                        return true;
                    };
                }
            }
            tempData.add(tempNode);
            tempNode = tempNode.next;
        }
        return false;
    }
}