[数据结构与算法]双向链表的建立，插入，删除

#include <iostream>
using namespace std;
struct link
{
    double num;
    link* next;
    link* front;
};
int main()
{
    link* p, * head;
    p = head = new link;
    //没有头结点的双向链表的建立
    for (int i = 0; i < 5; i++)
    {
        p->num = i;
        p->next = new link;
        p->next->front = p;
        p = p->next;
    }
    //双向链表的检验
    p = head;//正向输出
    for (int i = 0; i < 5; i++)
    {
        cout << p->num << endl;
        p = p->next;
    }
    p = p->front;//逆向输出
    for (int i = 4; i >= 0; i--)
    {
        cout << p->num << endl;
        p = p->front;
    }
    //双向链表的插入
    p = head;
    link* t = new link;
    t->num = 10;
    p->next->front = t;
    t->next = p->next;
    p->next = t;
    t->front = p;
    //双向链表的插入检验
    p = head;
    for (int i = 0; i < 6; i++)
    {
        cout << p->num << endl;
        p = p->next;
    }
    //双向链表的删除
    p = head;
    for (int i = 0; i < 6; i++)
    {
        if (p->num == 2)
        {
            p->front->next = p->next;
            p->next->front = p->front;
            delete p;
            break;
        }
        p = p->next;
    }
    //双向链表的删除的检验
    p = head;
    for (int i = 0; i < 5; i++)
    {
        cout << p->num << endl;
        p = p->next;
    }

    //删除所有节点
    link* a = head;
    p = head;
    for (int i = 0; i < 5; i++) {
        p = p->next;
        delete a;
        a = p;
    }
}