Given a linked list, return the node where the cycle begins. If there is no cycle, return null.
To represent a cycle in the given linked list, we use an integer pos which represents the position (0-indexed) in the linked list where tail connects to. If pos is -1, then there is no cycle in the linked list.
Note: Do not modify the linked list.
/** * Definition for singly-linked list. * class ListNode { * int val; * ListNode next; * ListNode(int x) { * val = x; * next = null; * } * } */ public class Solution { public ListNode detectCycle(ListNode head) { if (head == null || head.next == null) { return null; } ListNode fast = head; ListNode slow = head; while(fast != null && fast.next != null) { slow = slow.next; fast = fast.next.next; if (slow == fast) { // get the entry point when cur and slow meet ListNode cur = head; while(cur != slow) { cur = cur.next; slow = slow.next; } return slow; } } return null; } }
[LC] 142. Linked List Cycle II
原文：https://www.cnblogs.com/xuanlu/p/12066983.html