数据结构复习 之 一个简单双向链表的实现

1. 什么时候能默写出来呢？

#include <iostream>

using namespace std;
struct node
{
    int data;
    node *next;
    node *prior;
};



class Link
{
    public:
    Link()
    {
        head_ptr = NULL;
        tail_ptr = NULL;

    }
    void insertNode();
    void insertNode(node *ptr);
    void insertNodeAtHead(node *ptr);
    void insertNodeAtTail(node *ptr);
    void deleteNodeAtHead();
    void deleteNodeAtTail();

    void showList();
    void findData(int data);
    private:
    node * head_ptr;
    node * tail_ptr;
};

void Link::insertNode()
{
    node * p = new node;
    int data;
    if(p != NULL)
    {
        cin >> data;
        p->data = data;
        p->next = NULL;
        p->prior = NULL;
    }
    insertNode(p);
}
void Link::insertNode(node *ptr)
{
    node * current_ptr;
    if(head_ptr == NULL)
    {
        head_ptr = ptr;
        tail_ptr = ptr;
        return;
    }
    if(head_ptr->next == NULL)
    {
        if(ptr->data < head_ptr->data)
        insertNodeAtHead(ptr);

        else
        insertNodeAtTail(ptr);
        return;
    }
    if(head_ptr->next != NULL)
    {
        current_ptr = head_ptr;
        while(current_ptr != NULL
               && ptr->data > current_ptr->data)
               {
                   current_ptr = current_ptr->next;
               }
               if(current_ptr == head_ptr)
               insertNodeAtHead(ptr);
               else if(current_ptr == NULL)
               insertNodeAtTail(ptr);
               //如果没有查找完整个表，并且满足排序条件的
               //输出，欲插入的节点应该插入到current_ptr之前
               else
               {
                   ptr->next = current_ptr;
                   ptr->prior = current_ptr->prior;
                   current_ptr->prior->next = ptr;
                   current_ptr->prior = ptr;
               }
               return;
    }


}

void Link::insertNodeAtHead(node *ptr)
{
    ptr->next = head_ptr;
    ptr->prior = NULL;
    head_ptr->prior = ptr;
    head_ptr = ptr;
}
void Link::insertNodeAtTail(node *ptr)
{
    ptr->prior = tail_ptr;
    ptr->next = NULL;
    tail_ptr->next = ptr;
    tail_ptr = ptr;
}

void Link::showList()
{
    node *current_ptr = head_ptr;
    if(current_ptr == NULL)
    {
        cout << "链表为空" << endl;
        return;
    }
    while(current_ptr != NULL)
    {
        cout << current_ptr->data << " ";
        current_ptr = current_ptr->next;
    }
    cout << endl;
}
void Link::deleteNodeAtHead()
{
    if(head_ptr->next == NULL)
    {
          delete head_ptr;
          head_ptr = tail_ptr = NULL;
    }
    node *current_ptr = head_ptr;
    head_ptr = head_ptr->next;
    head_ptr->prior = NULL;
    delete current_ptr;


}
void Link::deleteNodeAtTail()
{
    node * current_ptr =tail_ptr;
    tail_ptr = tail_ptr->prior;
    tail_ptr->next = NULL;
    delete current_ptr;
}

void Link::findData(int data)
{
    if(head_ptr == NULL)
    {
        cout << "链表为空" << endl;
    }
    int count = 0;
    node * current_ptr = head_ptr;
    while(data > current_ptr->data  && current_ptr->next != NULL)
    {
        current_ptr = current_ptr->next;
        count ++;
    }
    if(current_ptr != NULL)
    cout << "已经找到元素,在第" << count << "位" << endl;
    else
    cout << " 没有找到,不存在" << endl;


}

int main()
{
    Link link;
    for(int i = 0;i < 10;i ++)
    link.insertNode();


    link.showList();

    link.deleteNodeAtHead();
    link.showList();
    link.deleteNodeAtTail();
    link.showList();

    link.findData(5);
    return 0;
}