环形链表问题

Posted 2022-02-05 Alice_yufeng

/**
 * 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) 
        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;