package code; /* * 141. Linked List Cycle * 题意：链表是否有环 * 难度：Easy * 分类：Linked List, Two Pointers * 思路：快慢指针 * lc142 */ public class lc141 { public class ListNode { int val; ListNode next; ListNode(int x) { val = x; } } public boolean hasCycle(ListNode head) { if(head==null||head.next==null) return false; ListNode slow = head; ListNode fast = head.next; while(fast!=null&&fast.next!=null){ //注意判断条件，slow一定不等于null，不用判断了 slow = slow.next; fast = fast.next.next; if(fast==slow) return true; } return false; } }