题目:给定单向链表的头指针和一个结点指针,定义一个函数在O(1)时间删除该结点。链表结点与函数的定义如下:
思路:设这个要删除的结点指针为i,找到该结点的下一结点j,然后将j的内容复制给i,并将i的指针指向j的下一结点,然后将j结点删除。这样的效果就是把i结点删除;
但是如果要删除的结点在链表尾部,那它就没有下一结点。所以也需要从链表的头结点开始,顺序遍历得到该结点的前序结点,然后完成删除操作;
如果链表中只有一个结点,在删除之后,应该将链表的头结点设置为NULL。
测试用例:
1.功能测试:头、尾、中间结点、唯一结点
2.特殊输入测试:NULL指针
#include<iostream>
#include<cstdio>
using namespace std;
struct ListNode
{
int m_nValue;
ListNode* m_pNext;
};
//创建链表结点
ListNode* CreateListNode(int value)
{
ListNode* pNode = new ListNode();
pNode->m_nValue = value;
pNode->m_pNext = NULL;
return pNode;
}
//连接链表节点
void ConnectListNodes(ListNode* pCurrent, ListNode* pNext)
{
if (pCurrent == NULL)
{
cout << "连接错误" << endl;
return;
}
pCurrent->m_pNext = pNext;
}
//打印链表
void PrintList(ListNode* pHead)
{
ListNode* pNode = pHead;
while (pNode != NULL)
{
cout << pNode->m_nValue << " ";
pNode = pNode->m_pNext;
}
cout << endl;
}
//销毁链表
void DestroyList(ListNode* pHead)
{
ListNode* pNode = pHead;
while (pNode != NULL)
{
pHead = pHead->m_pNext;
delete pNode;
pNode = pHead;
}
}
void DeleteNode(ListNode** pListHead, ListNode* pToBeDeleted)
{
if (!pListHead || !pToBeDeleted)
{
return;
}
//要删除的结点不是尾结点
if (pToBeDeleted->m_pNext != NULL)
{
ListNode* pNext = pToBeDeleted->m_pNext;
pToBeDeleted->m_nValue = pNext->m_nValue;
pToBeDeleted->m_pNext = pNext->m_pNext;
delete pNext;
pNext = NULL;
}
//链表只有一个结点,删除头结点(也是尾结点),删除之后设NULL
else if (*pListHead == pToBeDeleted)
{
delete pToBeDeleted;
pToBeDeleted = NULL;
*pListHead = NULL;
}
//链表中有多个结点,删除尾结点,遍历链表
else
{
ListNode* pNode = *pListHead;
while (pNode->m_pNext != pToBeDeleted)
{
pNode = pNode->m_pNext;
}
pNode->m_pNext = NULL;
delete pToBeDeleted;
pToBeDeleted = NULL;
}
}
//测试
void test1()
{
ListNode* pNode1 = CreateListNode(1);
ListNode* pNode2 = CreateListNode(2);
ListNode* pNode3 = CreateListNode(3);
ListNode* pNode4 = CreateListNode(4);
ListNode* pNode5 = CreateListNode(5);
ConnectListNodes(pNode1, pNode2);
ConnectListNodes(pNode2, pNode3);
ConnectListNodes(pNode3, pNode4);
ConnectListNodes(pNode4, pNode5);
PrintList(pNode1);
DeleteNode(&pNode1, pNode5);
PrintList(pNode1);
DeleteNode(&pNode1, pNode2);
PrintList(pNode1);
DeleteNode(&pNode1, pNode1);
PrintList(pNode1);
DestroyList(pNode1);
}
void test2()
{
ListNode* pNode1 = CreateListNode(1);
PrintList(pNode1);
DeleteNode(&pNode1, pNode1);
PrintList(pNode1);
}
void test3()
{
PrintList(NULL);
DeleteNode(NULL, NULL);
PrintList(NULL);
}
int main()
{
test1();
test2();
test3();
}