LeetCode-141 Linked List Cycle Solution (with Java)

1. Description: 

Notes:

2. Examples: 

3.Solutions:

/**
 * Created by sheepcore on 2019-05-14
 * Definition for singly-linked list.
 * class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public boolean hasCycle(ListNode head) {
    ListNode p = head,pre = head;
    while(p != null && p.next != null){
        if (p.next == head) return true;
        p = p.next;
        pre.next = head;
        pre = p;
    }
    return false;
}