题解 | #链表中环的入口结点#
链表中环的入口结点
https://www.nowcoder.com/practice/253d2c59ec3e4bc68da16833f79a38e4
/* public class ListNode { int val; ListNode next = null; ListNode(int val) { this.val = val; } } */ public class Solution { public ListNode EntryNodeOfLoop(ListNode pHead) { if (pHead == null) { return null; } ListNode fast = pHead; ListNode slow = fast; while (fast != null && fast.next != null) { fast = fast.next.next; slow = slow.next; if (fast == slow ) { break; } } // 不存在环 if (fast == null || fast.next == null) { return null; } // ListNode second = pHead; //指针重新回到表头 ListNode second = pHead; //再次相遇即是环入口 while (second != slow) { second = second.next; slow = slow.next; } return slow; } }