leetcode01 --- 环形链表判定

题目

. - 力扣（LeetCode） 环形链表判定

代码

/**
 * 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) {
        ListNode node = head;
        ListNode preNode = head;
        while (node.next != null) {
            boolean cycle = false;
            while (preNode != node) {
//                System.out.println("val = " + preNode.val);
                if (node.next == preNode) {
                    return true;
                }
                preNode = preNode.next;
            }
//            System.out.println("cycle = " + cycle);
            //if (cycle) {
            //    return true;
            //}
            node = node.next;
            preNode = head;
        }
        return false;
    }
}