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【面试题013】在O(1)时间删除链表结点

2014-04-29 08:47 218 查看

【面试题013】在O(1)时间删除链表结点

我们要删除结点i，我们可以把结点i的下一个结点j的内容复制到结点i，然后呢把结点i的指针指向结点j的下一个结点。然后在删除结点j。

1.如果结点i位于链表的尾部；

2.如果结点i位于链表的头部；

3.如果结点i既是链表的头部又是链表的尾部；

DeleNode.cpp:

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#include <iostream>
#include <cstdio>
#include "List.h"

using namespace std;

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）*/
else if (*pListHead == pToBeDeleted)
{
delete pToBeDeleted;
pToBeDeleted = NULL;
*pListHead = NULL;
}
/*链表中有多个节点呢，删除尾结点*/
else
{
ListNode *pNode = *pListHead;
while(pNode->m_pNext != pToBeDeleted)
{
pNode = pNode->m_pNext;
}
pNode->m_pNext = NULL;
delete pToBeDeleted;
pToBeDeleted = NULL;
}

}

// 链表中有多个结点，删除中间的结点
int main()
{
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);

ListNode *pListHead = pNode1;
ListNode *pNode = pNode3;

printf("The original list is: \n");
PrintList(pListHead);

printf("The node to be deleted is: \n");
PrintListNode(pNode);

DeleteNode(&pListHead, pNode);

printf("The result list is: \n");
PrintList(pListHead);

DestroyList(pNode1);

return 0;
}

运行结果：

The original list is:

PrintList starts.
1 2 3 4 5
PrintList ends.
The node to be deleted is:
The key in node is 3.
The result list is:
PrintList starts.
1 2 4 5
PrintList ends.

List.h:

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#ifndef _LIST_H_
#define _LIST_H_

struct ListNode
{
int m_nValue;
ListNode *m_pNext;
};

ListNode *CreateListNode(int value);
void ConnectListNodes(ListNode *pCurrent, ListNode *pNext);
void PrintListNode(ListNode *pNode);
void PrintList(ListNode *pHead);
void DestroyList(ListNode *pHead);
void AddToTail(ListNode **pHead, int value);
void RemoveNode(ListNode **pHead, int value);

#endif //_LIST_H_

List.cpp:

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#include "list.h"
#include <stdio.h>
#include <stdlib.h>

ListNode *CreateListNode(int value)
{
ListNode *pNode = new ListNode();
pNode->m_nValue = value;
pNode->m_pNext = NULL;

return pNode;
}

void ConnectListNodes(ListNode *pCurrent, ListNode *pNext)
{
if(pCurrent == NULL)
{
printf("Error to connect two nodes.\n");
exit(1);
}

pCurrent->m_pNext = pNext;
}

void PrintListNode(ListNode *pNode)
{
if(pNode == NULL)
{
printf("The node is NULL\n");
}
else
{
printf("The key in node is %d.\n", pNode->m_nValue);
}
}

void PrintList(ListNode *pHead)
{
printf("PrintList starts.\n");

ListNode *pNode = pHead;
while(pNode != NULL)
{
printf("%d\t", pNode->m_nValue);
pNode = pNode->m_pNext;
}

printf("\nPrintList ends.\n");
}

void DestroyList(ListNode *pHead)
{
ListNode *pNode = pHead;
while(pNode != NULL)
{
pHead = pHead->m_pNext;
delete pNode;
pNode = pHead;
}
}

void AddToTail(ListNode **pHead, int value)
{
ListNode *pNew = new ListNode();
pNew->m_nValue = value;
pNew->m_pNext = NULL;

if(*pHead == NULL)
{
*pHead = pNew;
}
else
{
ListNode *pNode = *pHead;
while(pNode->m_pNext != NULL)
pNode = pNode->m_pNext;

pNode->m_pNext = pNew;
}
}

void RemoveNode(ListNode **pHead, int value)
{
if(pHead == NULL || *pHead == NULL)
return;

ListNode *pToBeDeleted = NULL;
if((*pHead)->m_nValue == value)
{
pToBeDeleted = *pHead;
*pHead = (*pHead)->m_pNext;
}
else
{
ListNode *pNode = *pHead;
while(pNode->m_pNext != NULL && pNode->m_pNext->m_nValue != value)
pNode = pNode->m_pNext;

if(pNode->m_pNext != NULL && pNode->m_pNext->m_nValue == value)
{
pToBeDeleted = pNode->m_pNext;
pNode->m_pNext = pNode->m_pNext->m_pNext;
}
}

if(pToBeDeleted != NULL)
{
delete pToBeDeleted;
pToBeDeleted = NULL;
}
}

Makefile:

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.PHONY:clean
CPP=g++
CFLAGS=-Wall -g
BIN=test
OBJS=DeleNode.o List.o
LIBS=
$(BIN):$(OBJS)
$(CPP) $(CFLAGS) $^ -o $@ $(LIBS)
%.o:%.cpp
$(CPP) $(CFLAGS) -c $< -o $@
clean:
rm -f *.o $(BIN)

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