LeetCode-Easy刷题(32) Linked List Cycle

Posted 2022-05-31 当以乐

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

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

给定一个链表，确定它是否有一个循环。  你能在不使用额外空间的情况下解决它吗?

 //两个速度指针
    public boolean hasCycle(ListNode head) 

       if(head ==null)
           return false;
       
       ListNode walker = head;
       ListNode runner = head;
       while(runner!=null && runner.next!=null)

           walker = walker.next;
           runner = runner.next.next;
           if(walker == runner)
               return true;
           
       
       return false;