https://leetcode-cn.com/problems/linked-list-cycle/
- 哈希指针
public static boolean hasCycle(ListNode head) {
Set<ListNode> set = new HashSet<>();
while (head!=null){
if(!set.add(head)){
return true;
}
head=head.next;
}
return true;
}
- 快慢指针
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;
}
}
