两种方式:
一、通过java中的集合类HashSet来解决问题
public class Solution {
public boolean hasCycle(ListNode head) {
Set<ListNode> seen = new HashSet<ListNode>();
while (head != null) {
if (!seen.add(head)) {
return true;
}
head = head.next;
}
return false;
}
}
二、通过快慢指针的方法来做
public class Solution {
public boolean hasCycle(ListNode head) {
if (head == null || head.next == null) {
return false;
}
ListNode slow = head;
ListNode fast = head.next;
while (slow != fast) {
if (fast == null || fast.next == null) {
return false;
}
slow = slow.next;
fast = fast.next.next;
}
return true;
}
}
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