在O(1)时间内删除链表结点 【微软面试100题 第六十题】

#include <iostream>
#include <stack>

using namespace std;

typedef struct ListNode
{
struct ListNode *next;
int data;
}ListNode;

void InitList(ListNode **head1,ListNode **toBeDelete);
void DeleteListNode(ListNode **pHead,ListNode *pToBeDelete);
void PrintList(ListNode *list);

int main(void)
{
ListNode *h,*toBeDelete;

InitList(&h,&toBeDelete);
PrintList(h);
cout <<"删除5" << endl;
DeleteListNode(&h,toBeDelete);
PrintList(h);

return 0;
}
void PrintList(ListNode *list)
{
while(list!=NULL)
{
cout << list->data << "->";

list = list->next;
}
cout << "NULL";
cout <<endl;
}
void DeleteListNode(ListNode **pHead,ListNode *pToBeDelete)
{
if(!pHead || !(*pHead) || !pToBeDelete)
return ;
//情况1
if(*pHead==pToBeDelete && pToBeDelete->next != NULL)
{
*pHead = pToBeDelete->next;
delete pToBeDelete;
}
//情况4
else if(pToBeDelete->next != NULL)
{
ListNode *pNext = pToBeDelete->next;
pToBeDelete->data = pNext->data;
pToBeDelete->next = pNext->next;
delete pNext;
pNext = NULL;
}
//情况2
else if(*pHead==pToBeDelete)
{
delete pToBeDelete;
pToBeDelete = NULL;
*pHead = NULL;
}
//情况3
else
{
ListNode *pNode = *pHead;
while(pNode->next != pToBeDelete)
pNode = pNode->next;
pNode->next = NULL;
delete pToBeDelete;
pToBeDelete = NULL;
}
}
//head:1-->5-->9-->NULL
void InitList(ListNode **head1,ListNode **toBeDelete)
{
ListNode *tmp = new ListNode;
tmp->data = 1;
*head1 = tmp;

tmp = new ListNode;
tmp->data = 5;
(*head1)->next = tmp;
*toBeDelete = tmp;

ListNode *tmp1 = new ListNode;
tmp1->data = 9;
tmp1->next = NULL;
tmp->next = tmp1;
}