双链表的创建、测长、打印、插入和删除

内容RT，实现代码如下所示：

#include <iostream>
#include <stdio.h>
#include <string>

using namespace std;

typedef struct student
{
  int data;
  struct student *next;
  struct student *pre;
}dnode;

// 建立双链表
dnode *creat()
{
  dnode *head, *p, *s;
  int x, cycle = 1;
  head = new dnode;
  p = head;

  while (cycle)
  {
    cout << "Please input data for dnode : ";
    cin >> x;

    if (x != 0)
    {
      s = new dnode;
      s->data = x;
      cout << x << endl;

      p->next = s;
      s->pre = p;
      p = s;
    } 
    else
    {
      cycle = 0;
    }
  }

  head = head->next;
  head->pre = NULL;
  p->next = NULL;

  //cout << "Head data of dnode is " << head->data << endl;
  return head;
}

//链表插入
dnode *Insert(dnode *head, int num)
{
  dnode *p0, *p1;
  p0 = new dnode;
  p0->data = num;
  p1 = head;

  while (p0->data > p1->data && p1->next != NULL)
  {
    p1 = p1->next;
  }

  if (p0->data <= p1->data)
  {
    if (p1 == head)// 头节点插入
    {
      p0->next = p1;
      p1->pre = p0;
      head = p0;
    } 
    else//中间结点插入
    {
      p1->pre->next = p0;
      p0->next = p1;
      p0->pre = p1->pre; // 遗忘点
      p1->pre = p0;
    }
  } 
  else// 尾部插入结点
  {
    p1->next = p0;
    p0->pre = p1;
    p0->next = NULL;
  }
  return head;
}

// 双链表删除
dnode *del(dnode *head, int num)
{
  dnode *p1;
  p1 = head;

  while (num != p1->data && p1->next != NULL)
  {
    p1 = p1->next;
  }

  if (p1->data == num)
  {
    if (p1 == head)//首结点 head head->next 
    {
      head = head->next;
      head->pre = NULL;
      delete p1;
    } 
    else
    {
      if (p1->next == NULL)// 尾节点 p1->pre  p1  NULL
      {
        p1->pre->next = NULL;
        delete p1;
      } 
      else//中间结点
      {
        p1->next->pre = p1->pre;
        p1->pre->next = p1->next;
        delete p1;
      }
    }
  } 
  else
  {
    cout << "Please check out the data !" << endl;
  }
  return head;
}

// 打印双链表
void PrintDL(dnode *head)
{
  dnode *p = head;
  int l = 0;

  while (p != NULL)
  {
    p = p->next;
    l++;
  }
  cout << "The length of dnode is " << l << endl;

  p = head;
  for (int i = 0; i < l; i++)
  {
    cout << "The dnode data is " << p->data << endl;
    p = p->next;
  }

}

int main()
{
  cout << "****创建双链表****" << endl;
  dnode *head = creat();
  cout << endl;

  cout << "****双链表测长和打印****" << endl;
  PrintDL(head);
  cout << endl;

  cout << "***双链表插入数据***" << endl;
  cout << "Please input the int data for ins operate : ";
  int Indata1 = 0;
  cin >> Indata1;
  head = Insert(head, Indata1);
  PrintDL(head);
  cout << endl;

  cout << "***双链表删除数据***" << endl;
  cout << "Please input the int data for del operate : ";
  int Indata2 = 0;
  cin >> Indata2;
  head = del(head, Indata2);
  PrintDL(head);
  cout << endl;

  return 0;
}

1.头结点插入和删除

2.中间结点插入和删除

3.尾结点插入和删除