遍历自定义双链表

Question

我正在实现一个双链表。我已经实现了添加到列表头部和尾部的功能。我一直在尝试制作一个可以打印给定对象的所有元素的函数。 尽管该函数会打印第一个值，但它不会打印列表中的任何其他项目。

d_list.h

 #include<iostream>
 #include "node.h"

 #ifndef NODE_H
 #define NODE_H


template<class T>
class d_list{
   private:
       int l_size;
       Node<T>* head;
       Node<T>* tail;

   public:
       d_list():l_size(0){
          head=nullptr;
          tail=nullptr;
       }
       Node<T>* gethead(){return this->head;}
       Node<T>* gettail(){return this->tail;}

         int getlength(){
           return this->l_size;
         }

       void addashead(T data){
          Node<T>* curr_node=new Node<T>(data);
          if(this->head==nullptr){
            this->head=curr_node;
            this->tail=curr_node;
            this->l_size=l_size+1;
          }else {
             curr_node->next=this->head->previous;
              this->head->previous=curr_node;
             this->head=curr_node;

              this->l_size=l_size+1;
          }
       }

       void addastail(T data ){
          Node<T>* curr_node=new Node<T>(data);
          if(this->tail==this->head){
            this->head->next=curr_node->previous;
            curr_node->previous=this->head;
            this->tail=curr_node;
            this->tail->next=nullptr;
            this->l_size=l_size+1;
          }
          else{
            this->tail->next=curr_node;
            curr_node->previous=this->tail;
            this->tail=curr_node;
            this->l_size=l_size+1;
          }
       }

       Node<T>* begin(){
         return this->head;
       }

       Node<T>* end(){
         return this->tail;
       }

       bool isempty(){
         return this->head==nullptr;
       }

       T& back(){
         return this->tail->m_data;
       }

       T& front(){
         return this->head->m_data;
       }

       void printlist(){
           Node<T>* temp= this->head;
        while(temp) {
        std::cout << temp->m_data<< " -> ";
        temp = temp->next;
    }


       }

};

#endif

节点.h

template <class T>
class Node{
    private:


    public:
       T m_data;
       Node<T>* next;
       Node<T>* previous;
        Node()=default;
        Node(T data){
           m_data=data;
           previous=nullptr;
           next=nullptr;
        }
       ~Node();


};

main.cpp

#include "d_list.h"

#include<iostream>
using namespace std;



int main(){

    d_list<int> d1;


    d1.addashead(50);



    d1.addastail(20);


    d1.addastail(60);



    d1.addastail(80);



    d1.printlist();
    return 0;
}

Answer 1

你的 addastail() 和 addashead() 方法有一些错误。

我删除了这些错误，检查一下：

 void addashead(T data){
          Node<T>* curr_node=new Node<T>(data);
          if(this->head==nullptr){
            this->head=curr_node;
            this->tail=curr_node;
            this->l_size=l_size+1;
          }else {
             curr_node->next=this->head;
              this->head->previous=curr_node;
             this->head=curr_node;
             this->l_size=l_size+1;
           }

   }

在else部分的第一行， 你写道：

curr_node->next=this->head->previous;

但应该是：curr_node->next=this->head;

因为 curr_node 的下一个应该指向头部，而不是头部的上一个。

void addastail(T data ){
          Node<T>* curr_node=new Node<T>(data);
          if(this->tail==this->head){
            this->head->next=curr_node;
            curr_node->previous=this->head;
            this->tail=curr_node;
            this->tail->next=nullptr;
            this->l_size=l_size+1;
          }
          else{
            this->tail->next=curr_node;
            curr_node->previous=this->tail;
            this->tail=curr_node;
            this->l_size=l_size+1;
          }
       }

在if部分的第一行，你写了：

this->head->next=curr_node->previous;

但应该是：this->head->next=curr_node;