Linked List Cycle

Posted 2022-12-03 大数据最好

问题描述:

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

Follow up:
Can you solve it without using extra space?

代码实现：

/**
 * 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) return false;
        ListNode fast=head;
        ListNode slow=head;
        
        do
            if(fast!=null) fast=fast.next;
            if(slow!=null) slow=slow.next;
            if(fast != null)
                fast=fast.next;
            else
                return false;
            
        while(fast != slow);
        return true;