题解 | #链表中环的入口结点#

package main

func EntryNodeOfLoop(pHead *ListNode) *ListNode {
	reverseHead := &ListNode{}

	for pHead != nil {
		if pHead.Next == nil {
			return nil
		}
		// 判断自环
		if pHead.Next == pHead {
			return pHead
		}
		// 判断环
		if pHead.Next.Next == reverseHead {
			return pHead.Next
		}

		temp := pHead.Next
		pHead.Next = reverseHead
		pHead = temp
	}
	return nil
}