C++双向链表

　　本文C++实现的关于双向链表的增删查改操作，收获颇多，第一篇博客请多指教。

定义节点类型

1 struct Number{
2     int data;
3     Number* next;
4     Number* previous;
5 };

定义一个链表类

class LinkList{
private:
    Number *head;
    Number *tail;
    int length;
public:
    LinkList();
    
    void headInsert(int data);
    void tailInsert(int data);
    void display_HeadToTail();
    void display_TailToHead();
    Number * findNumber(int data);
    void change(Number*);
    void quit();
};

构造函数

LinkList::LinkList(){
    head = NULL;
    tail = head;
    length = 0;
}

头插函数

void LinkList::headInsert(int data){
    Number * node = new Number();
    node->data=data;
    if(head!=NULL){
        head->previous=node;
        node->next=head;
        node->previous=NULL;
        head=node;
    }
    else{
        head=tail=node;
        node->next=NULL;
        node->previous=NULL;
    }
    length++;
}

尾插函数

void LinkList::tailInsert(int data){
    
    Number * node = new Number();
    node->data=data;
    if(tail!=NULL){
        tail->next=node;
        node->previous=tail;
        node->next=NULL;
        tail=node;
    }
    else{
        tail=head=node;
        node->next=NULL;
        node->previous=NULL;
    }
    length ++;

}

正序遍历

void LinkList::display_HeadToTail(){
    Number *n = head;
    if(length==0){
        cout<<"No Number"<<endl;
        return;
    }
    cout<<"length: "<<length<<endl;
    cout<<"data:   ";
    while (n) {
        cout<<n->data<<" ";
        n = n->next;
    }
    cout << endl;
}

逆序遍历

void LinkList::display_TailToHead(){
    Number *n = tail;
    if(length==0){
        cout<<"No Number"<<endl;
        return;
    }
    cout<<"length: "<<length<<endl;
    cout<<"data:   ";
    while (n) {
        cout<<n->data<<" ";
        n = n->previous;
    }
    cout << endl;
}

查找节点

Number * LinkList::findNumber(int data){
Number * n = head;
while (n) {
if(n->data==data)
return n;
n = n->next;
}
return NULL;
}

修改节点（可以将 findNumber 的返回值作为参数传入）

void LinkList::change(Number* node){
    if(node==NULL)
    {
        cout<<"Number not exist"<<endl;
        system("pause");
        system("cls");
        return;
    }
    int data;
    cout<<"Enter a new data for "<<node->data<<" : ";
    cin>>data;
    system("cls");
    node->data=data;
}

删除节点

void LinkList::deleteNumber(Number  * n){
    if(n==NULL){
        cout<<"Node not exist"<<endl;
        return;
    }
    if(n==head)
        head=n->next;
    else
        n->previous->next=n->next;
    
    if(n==tail)
        tail=n->previous;
    else
        n->next->previous=n->previous;
    
    n->next=NULL;
    n->previous=NULL;
    delete(n);
}

删除所有节点

void LinkList::quit(){
    while(head){
        deleteNumber(head);
    }
    head=tail=NULL;
        length=0;
}

收获：

new和delete用法

malloc和free的用法

　　参考：https://www.cnblogs.com/maluning/p/7944231.html

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