数据结构 《3》----双向链表（带有头节点）

// copyright @ L.J.SHOU Jan.15, 2014
// double-linked-list with a head node
#include "double-linked-list.h"
#include <iostream>
using namespace std;

struct ListNode{
ListNode *pre;
ListNode *next;
int val;
ListNode(int x=0)
: val(x), pre(NULL), next(NULL){}
};

// return pointer to a head node
// list->val------length of list
// list->pre------the last node of list
// list->next---- the first node of list
ListNode* NewList()
{
return new ListNode(0);
}

ListNode* Destroy(ListNode *list)
{
ListNode *next(NULL);

while(list){
next = list->next;
delete list;
list = next;
}

return NULL;
}

// actually, no need to return head node's pointer
// since heading node never change
ListNode* Insert(ListNode *list, int x)
{
ListNode *pre(list), *cur(list->next);
ListNode *node(NULL);

while(cur && cur->val < x)
{
pre = cur;
cur = cur->next;
}
if(cur && cur->val == x) return list;

node = new ListNode(x);
node->next = cur;
pre->next = node;

// insert at first
if(pre != list)
node->pre = pre;
else
node->pre = NULL;
//insert at rear
if(cur != NULL)
cur->pre = node;
else
list->pre = node;

list->val ++; // length++

return list;
}

ListNode* Delete(ListNode *list, int x)
{
ListNode *pre(list), *cur(list->next);

while(cur && cur->val != x)
{
pre = cur;
cur = cur->next;
}

if(cur && cur->val == x)
{
pre->next = cur->next;

//最后一个节点删除单独处理(相当与首节点删除)
if(cur->next != NULL)
cur->next->pre = cur->pre; //cur->pre 而不是 pre
else
list->pre = cur->pre;

delete cur;
--list->val;
}
return list;
}

void PrintList(ListNode *list)
{
cout << "Length of list: " << list->val << endl;
list = list->next;
while(list){
cout << list->val << " ";
list = list->next;
}
cout << endl;
}

void ReversePrintList(ListNode *list)
{
list = list->pre;
while(list){
cout << list->val << " ";
list = list->pre;
}
cout << endl;
}

int main(void)
{
ListNode *list = NewList();

for(int i=10; i>0; --i)
list = Insert(list, i);
list = Delete(list, 1);
list = Delete(list, 5);
list = Delete(list, 10);
PrintList(list);
ReversePrintList(list);

list = Destroy(list);

return 0;
}