单链表

#include<iostream>

using namespace std;

struct Node
{
    int val;
    Node* next;

    Node():next(NULL){};
    Node(int _val): val(_val),next(NULL){}
};

void print(Node* head){
    for(auto p = head;p;p = p->next){
        cout << p->val <<" ";
    }
    cout << endl;
}

int main()
{
    Node* head = new Node(1);// head -> 1

    auto a = new Node(2);
    head->next = a;// head -> 1 -> 2

    auto b = new Node(3);
    a->next = b;// head -> 1 -> 2 -> 3  

    auto c = new Node(4);
    c->next = head->next;//head->1->4->2->3
    head->next = c;

    c->next = c->next->next;//head->1->4->3
    delete a;

    //删除第一个点
    auto p = head;
    head = head->next;
    delete p;//head->4->3
    print(head);
    return 0;
}

双链表

#include<iostream>

using namespace std;

struct Node
{
    int val;
    Node *prev,*next;

    Node():prev(NULL),next(NULL){};
    Node(int _val): val(_val),prev(NULL),next(NULL){}
};

void print(Node* head){
    for(auto p = head;p;p = p->next)
        cout << p->val <<" ";
    cout << endl;
}

int main()
{
    //哨兵
    Node *head = new Node(),*tail = new Node();
    head->next = tail,tail->prev = head;

    print(head);//0 0 

    //第一个位置插入一个节点
    auto a = new Node(1);
    a->next = head->next,a->prev = head;
    head->next->prev = a,head->next = a;
    print(head);//0 1 0

    auto b = new Node(2);
    b->next = head->next,b->prev = head;
    head->next->prev = b,head->next = b;

    print(head);//0 2 1 0

    //将节点插入到某一个节点(b)点后边
    auto c = new Node(3);
    c->next = b->next,c->prev = b;
    b->next->prev = c,b->next = c;

    //删除掉某个点(b)
    b->next->prev = b->prev;
    b->prev->next = b->next;

    print(head);//0 3 1 0 

}

循环链表

#include<iostream>

using namespace std;

struct Node
{
    int val;
    Node *prev,*next;

    Node():prev(NULL),next(NULL){};
    Node(int _val): val(_val),prev(NULL),next(NULL){}
};

void print(Node* head){
    for(auto p = head->next;p != head;p = p->next)//循环链表遍历到头就是结束
        cout << p->val <<" ";
    cout << endl;
}

int main()
{
    //哨兵 没用
    Node *head = new Node(),*tail = head;
    head->next = tail,tail->prev = head;

    print(head);//0 0 

    //第一个位置插入一个节点
    auto a = new Node(1);
    a->next = head->next,a->prev = head;
    head->next->prev = a,head->next = a;
    print(head);//0 1 0

    auto b = new Node(2);
    b->next = head->next,b->prev = head;
    head->next->prev = b,head->next = b;

    print(head);//0 2 1 0

    //将节点插入到某一个节点(b)点后边
    auto c = new Node(3);
    c->next = b->next,c->prev = b;
    b->next->prev = c,b->next = c;

    //删除掉某个点(b)
    b->next->prev = b->prev;
    b->prev->next = b->next;

    print(head);//0 3 1 0 

}