在O时间删除链表某一节点

Posted 2022-12-14 ssopp24

给定单链表头节点和一个结点指针，在O(1)时间删除该结点。

struct ListNode

	int	m_nValue;
	ListNode* m_pNext;
;

void DeleteNode( ListNode** pListHead, ListNode* pToBeDeleted )

	//1.链表为空
	if ( NULL == *pListHead || NULL == pToBeDeleted )
		return;

	//2.链表只有一个结点						//O(1)
	if ( *pListHead == pToBeDeleted )
	
		delete pToBeDeleted;
		pToBeDeleted = NULL;
		*pListHead = NULL;

		return;
	

	//3.被删除结点为链表尾节点					//O(N)
	if ( NULL == pToBeDeleted->m_pNext )
	
		ListNode* pPrev = *pListHead;

		while ( pToBeDeleted != pPrev->m_pNext )
			pPrev = pPrev->m_pNext;

		delete pToBeDeleted;
		pToBeDeleted = NULL;
		pPrev->m_pNext = NULL;

		return;
	

	//4.被删除结点是至少有两个结点的链表非尾节点//O(1)
	ListNode* pNext = pToBeDeleted->m_pNext;

	pToBeDeleted->m_nValue = pNext->m_nValue;
	pToBeDeleted->m_pNext = pNext->m_pNext;

	delete pNext;
	pNext = NULL;
	return;