双向链表的基本操作

双向链表的建立，打印，查找，增删

#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <climits>
using namespace std;
//以下是关于双链表的操作
struct dnode {
    int data;
    dnode* left;
    dnode* right;
    dnode() {
        data = 0;
        left = right = nullptr;
    }
    dnode(int d)
    {
        data = d;
        left = right = nullptr;
    }
};
//根据数据创建节点
//插入新节点，总在表尾部插入；返回表头节点
dnode* append_node(dnode* head, int data)
{
    dnode* node = new dnode(data);
    dnode* p = head, *q=nullptr;
    while (p != nullptr)
    {
        q = p;
        p = p->right;
    }
    q->right = node;
    node->left = q;
    return head;
}
dnode* creat_list()
{
    dnode* head = new dnode(0);
    for (int i = 1; i < 10; i++)
    {
        head=append_node(head, i);
    }
    return head;//这就是已经创建好的链表的表头
}
//实现双链表的测长
int get_length(dnode* head)
{
    int cnt = 0;
    dnode* pnode = head;
    while (pnode != nullptr)
    {
        cnt++;
        pnode = pnode->right;
    }
    return cnt;
}
//下面是打印整个链表、
void print_list(dnode* head)
{
    dnode* pnode = head;
    if (head == nullptr)
        return;
    while (pnode != nullptr)
    {
        printf("%d ", pnode->data);
        pnode = pnode->right;
    }
    printf("\n");
}
//双向链表的查找
dnode* find_node(dnode* head, int data)
{
    dnode* pnode = head;
    if (head == nullptr)
        return nullptr;
    while ( pnode->data != data)
    {
        if(pnode->right != nullptr)
        pnode=pnode->right;
    }

    return pnode;
}
//双向链表的插入：在节点node之后插入一个节点
void insert_node(dnode* node, int data)
{
    dnode* newnode = new dnode(data);
    if (node->right == nullptr)//在结尾插入新节点
    {
        node->right = newnode;
        newnode->left = node;
    }
    else//在中间的情况
    {
        newnode->right = node->right;
        node->right->left = newnode;
        node->right = newnode;
        newnode->left = node;
    }
}
//删除一个双向链表中的节点，返回表头节点，删除失效，返回nullptr
dnode* delete_node(dnode* head, int data)
{
    dnode* ptmp = nullptr;
    dnode* pnode = find_node(head, data);
    if (pnode == nullptr)
        return nullptr;//没有找到要删除的节点，返回null
    else if (pnode->left == nullptr)//找到的节点是首部节点
    {
        head = pnode->right;
        if (head != nullptr)
        {
            head->left = nullptr;
        }
    }
    else if (pnode->right == nullptr)//找到的节点是尾部节点
    {
        pnode->left->right = nullptr;
    }
    else//node为中间节点
    {
        pnode->left->right = pnode->right;
        pnode->right->left = pnode->left;
    }
    return head;
}
int main() {
    cout << "begin\n";
    dnode* head=creat_list();
    cout << "list length: " << get_length(head)<<endl;
    print_list(head);
    cout << "寻找特定节点：" << endl;
    dnode* p = find_node(head, 4);
    print_list(p);
    cout << "在特定节点后插入一节点13" << endl;
    insert_node(p, 13);
    print_list(head);
    cout << "删除特定的节点13" << endl;
    head=delete_node(head, 13);
    print_list(head);
    }