數據結構——雙向鏈表實現，基本操作的C++版

對於循環雙向鏈表

判斷一個鏈表是否爲空的條件爲：head->next==head (頭指針)

判斷*p爲最後一個節點的條件爲：p->next=head

#include<iostream>
using namespace std;

/*雙鏈表結構*/
typedef struct node
{
    int data;
    struct node *prior;
    struct node *next;

}DNode;
/*創建一個帶頭節點的雙鏈表*/
void CreateDLink(DNode *&head)
{
    int x;
    DNode *p,*s;
    s=(DNode *)malloc(sizeof(DNode));
    if(s==NULL)
    {
       cout<<"Fail to malloc the head node!"<<endl;
    }
       s->data=0;
       s->prior=NULL;
       s->next=NULL; //建立一個頭結點爲head的雙鏈表
    head=s;   //若是循環雙向鏈表則爲：s->next=s->prior=s;
    cout<<"please input the data of the node"<<endl;
    cin>>x;
    while(x!=0)
    {
      p=(DNode *)malloc(sizeof(DNode));
     if(p==NULL)
     {
        cout<<"Fail to malloc a new  node!"<<endl;
     }

     p->data=x;
     s->next=p;
     p->prior=s;
     p->next=NULL;
     s=p;

     cin>>x;
    }

}

void PrintLink(DNode *head)
{
    if(head->next==NULL)
    {
        cout<<"The list is NULL"<<endl;
        return ;
    }
    DNode *p;
    p=head->next;
    while(p!=NULL)
    {
        cout<<p->data<<" ";
        p=p->next;

    }
   cout<<endl;
}
int Length(DNode *head) //求雙鏈表長度
{
    int len=0;
    DNode * p=head->next;
    while(p!=NULL)
    {
        len++;
        p=p->next;
    }
    return len;

}
DNode * Get(DNode *head,int i) //獲取鏈表第i個節點地址
{
    int j=0;
    DNode *p=head->next;
    while(j<i&&p!=NULL)
    {
        p=p->next;
        j++;
    }
    if(p!=NULL)
        return p;
    else
        return NULL;
}
int InsertNode(DNode *head,int x,int i)//在第i個位置插入一個節點
{
    DNode *s,*p;
    s=(DNode *)malloc(sizeof(DNode));
    s->data=x;
    if(i==0)
    {
        s->next=head->next;
        if(head->next!=NULL)
            head->next->prior=s;
        s->prior=head;
        head->next=s;

    }
    else
    {
        p=Get(head,i-1); //查找待插入節點前一個位置
        if(p==NULL)
            return 0;
        else
        {
            s->next=p->next;
            if(p->next!=NULL)
                p->next->prior=s;
            s->prior=p;
            p->next=s;
        }
    }

    return 1;
}

void DeleteNode(DNode *head,int index) //刪除第index個節點
{
    if(head->next==NULL)
    {
        cout<<"The list is NULL"<<endl;
        return;
    }
    DNode *p,*s/*保存待刪除的節點*/;
    if(index==0)
    {
        s=head->next;
        head->next=s->next;
        if(s->next!=NULL)
            s->next->prior=head;
         free(s);
    }
    else
    {
        p=Get(head,index-1);
        if(p==NULL)
            cout<<"The Node "<<index<<"is not exist"<<endl;
        else
        {
            s=p->next;
            p->next=s->next;
            if(s->next!=NULL)
                s->next->prior=p;
            free(s);
        }
    }

}
int main(int argc,char *argv[])
{
  DNode *head;
  CreateDLink(head);
  cout<<"鏈表長度爲："<<Length(head)<<endl;
   PrintLink(head);
   cout<<"第3個節點的值爲:"<<Get(head,3)->data<<endl;

   cout<<"輸入插入節點的位置及值："<<endl;
    int value, index;
    cin>>index>>value;
   InsertNode(head,value,index);
   cout<<"插入後的鏈表爲："<<endl;
       PrintLink(head);

       cout<<"請輸入要刪除的節點位置："<<endl;
       cin>>index;
       DeleteNode(head,index);
   PrintLink(head);
    return 0;
}