单链表的升级--双向链表基操之插入操作和删除操作

1. 了解双向链表

• 看图思考什么是双向链表
  
• 理解
  • 它可以有若干个数据域，可以存储更多的有用的数据！
  • 它有两个指针域，一个指向它的前趋结点（pre），另一个指向它的后继结点（next）；
  • 它有优点：read、insert、delete更快了，空间换时间！

2. 双向链表的插入操作

• 目标
  把s结点插入到双向链表中
• 推演
  
• 代码

              #include<iostream>
              using namespace std;
              struct Node
              {
                  int data1, data2;
                  Node *pre, *next;
              };
              Node *head, *p, *q, *r;
              int x,y;
              int find(Node *head){
                  int n = 1;
                  p = head;
                  while (p != NULL)
                  {
                      n += 1;
                      p = p->next;
                  }
                  return n;
              }
              void insertD(Node *head, int i, int m)
              {
                  Node *s,*n;//定义两个Node指针
                  int j=0;//初值
                  s = new Node;//申请内存，s结点为新增插入的结点
                  s->data1 = m;//数据域赋值
                  n = head;//
                  while((n->next != NULL) && (j<i))
                  {
                      n = n->next;
                      j++;
                  }
                  if(n->next == NULL)
                      cout<< "没有位置了";
                  else
                  {
                      /* insert操作 */
                      n->pre->next = s;
                      s->pre = n->pre;
                      s->next = n;
                      n->pre = s;
                  }
              }
              int main(){
                  head = new Node;//
                  p = new Node;
                  q = new Node;
                  r = new Node;
                  head->next = p;
                  p->data1 = 1;
                  p->pre = head;
                  p->next = q;
                  q->data1 = 2;
                  q->pre = p;
                  q->next = r;
                  r->data1 = 3;
                  r->pre = q;
                  r->next = NULL;
                  cout << "这个双链表的结点数量为"<<find(head)<<"个"<<endl;
                  insertD(head,2,77);
                  cout << "这个双链表的结点数量为"<<find(head)<<"个"<<endl;
                  return 0;
              }
          
      
  

3. 双向链表的删除操作

• 目标
  

• 推演
  

• 代码

      #include<iostream>
      using namespace std;
      struct Node
      {
          int data1, data2;
          Node *pre, *next;
      };
      Node *head, *p, *q, *r;
      int x,y;
      int find(Node *head){
          int n = 1;
          p = head;
          while (p != NULL)
          {
              n += 1;
              p = p->next;
          }
          return n;
      }
      void MydeleteD(Node *head, int i)
      {
          Node *n;//
          int j;
          n = head;//
          j = 0;//初值
          while((n->next != NULL) && (j<i))
          {
              n = n->next;
              j++;
          }
          if(n->next == NULL)
              cout<< "没有位置了";
          else
          {
              /* delete操作 */
              n->pre->next = n->next;
              n->next->pre = n->pre;
          }
      }
      int main(){
          head = new Node;//
          p = new Node;
          q = new Node;
          r = new Node;
          head->next = p;
          p->data1 = 1;
          p->pre = head;
          p->next = q;
          q->data1 = 2;
          q->pre = p;
          q->next = r;
          r->data1 = 3;
          r->pre = q;
          r->next = NULL;
          cout << "这个双链表的结点数量为"<<find(head)<<"个"<<endl;
          MydeleteD(head,2);
          cout << "这个双链表的结点数量为"<<find(head)<<"个"<<endl;
          return 0;
      }
      ```
  

标签：pre,基操,head,--,Node,链表,int,new,next
来源： https://blog.csdn.net/qingdao_program/article/details/113830961