# 141. Linked List Cycle (Easy)

Given a linked list, determine if it has a cycle in it.

To represent a cycle in the given linked list, we use an integer `pos` which represents the position (0-indexed) in the linked list where tail connects to. If `pos` is `-1`, then there is no cycle in the linked list.

Example 1:

```Input: head = [3,2,0,-4], pos = 1
Output: true
Explanation: There is a cycle in the linked list, where tail connects to the second node.
``` Example 2:

```Input: head = [1,2], pos = 0
Output: true
Explanation: There is a cycle in the linked list, where tail connects to the first node.
``` Example 3:

```Input: head = , pos = -1
Output: false
Explanation: There is no cycle in the linked list.
``` Can you solve it using O(1) (i.e. constant) memory?

## Solutions

``````/**
* 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) {
while (head != null && head.next != null) {