题解 | #判断链表中是否有环#

/**
 * 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) {
        //定义快慢指针，如果有环的话就会相遇、
        ListNode f = head;
        ListNode s = head;
        while(f!=null&&f.next!=null){
            f = f.next.next;
            s = s.next;
            if(s==f){
                return true;
            }
        }
        return false;
        
    }
}