2

I know that the code below is quite simple, but I've been stuck on how to implement it for proper output. Feel so frustrated.

 struct node
 {
    node* p_next;
    int p_data;

    node(node* head, int data)
    {
        p_next = head;
        p_data = data;
    }

    explicit node(int data)
    {
        node(nullptr, data);
    }
 };

So I have this struct in C++ to construct some linked list.

Then I have insert function to insert some node to that linked list

 node* insert_node(node* head, int data)
 {
    return new node(head, data);
 }

Here I start getting dumb. How do I actually make some linked list with actual values out of this? I was confused how to construct a list first and add some values.

I've been trying the following but get errors.

struct node node_01(1);
node* node_ptr_01 = new node(1);

What I want to do.

  1. Create a head node with a value 10
  2. Keep adding values for other nodes with 20, 34, 32, 123, etc... random values for node

I do not know how to approach to initialize the pointer for head and add values on them.

Please help me. I would greatly appreciate it.

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3
  • 1
    Usually, you create a List class that uses your Node struct that handles inserting and deleting nodes from the list. The client code using the linked list will use your List class instead of manipulating Node directly. Commented Aug 21, 2013 at 3:58
  • You may find this presentation from Stanford to be informative. Commented Aug 21, 2013 at 4:29
  • Please read about the linked list concepts like add, delete and search. You need to keep keep Head as a start node, which should be global, frm then you have to play with it. Commented Aug 21, 2013 at 6:25

2 Answers 2

Reset to default
1

In your explicit constructor, the call to node(nullptr, data); is in local space and the result goes out of scope after the closing }.

Why can't you just save the values in this constructor (instead of calling the other one?):

explicit node(int data)
{
    p_next = nullptr;
    p_data = data;
}

By the way, your insert_node function works well:

int main() {

    // this testing code produces the correct result 
    // (assuming you fixed your explicit constructor):

    node node_01(9);
    node* node_ptr_01 = new node(1);

    cout << node_01.p_data << endl;
    cout << node_ptr_01->p_data << endl;

    node* n = insert_node(node_ptr_01, 5);
    cout << n->p_data;

    cin.get();
}
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1

Please go through how I have implemented linked list in c++ . I believe it will be simple to understand

This is Node.h

#ifndef _NODE_
#define _NODE_

class Node{


      private:

      char data;
      Node* next;
      void allocate();

      public:
      Node();
      char getData(void);
      Node*getNext();
      void setData(char data);
      void setNext(Node * next);
      ~Node();

      };

#endif

This is Node.cpp

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

Node::Node(): data('0'), next(NULL){

             std::cout<<"Node created"<<std::endl;
             }

void Node::setData(char data){

     this->data=data;
     }

void Node::setNext(Node *next){

     this->next=next;
     }    

char Node::getData(void){

     return data;
     }   

Node* Node:: getNext(void){

      return next;
      }

Node::~Node(){
              std::cout<<"Node deleted"<<std::endl;

              }

This is linkedList.h

#include"Node.h"

#ifndef Linked_
#define Linked_


class LinkedList{

      private:
           Node* head; 
           Node* createNode();  
           Node* getToLastNode();  
           int getLength();
           char getUserData();



           public:
                  LinkedList();
                  void addNodeAtTheBeginning();
                  void addNodeAtAGivenLocation(int);
                  void addNodeAtTheEnd();

                  void deleteFirstNode();
                  void deleteNodeAtAGivenLocation(int);
                  void deleteLastNode(); 
                  void display();
                  void deleteLinkedList();
                  ~LinkedList();


      };



#endif

This is LinkedList.cpp

#include"Node.h"
#include"LinkedList.h"
#include<iostream>


Node* LinkedList::createNode(){

      Node *tempNode;
      tempNode = new Node();
      tempNode->setNext(NULL);
      tempNode->setData(getUserData());
      return tempNode;   

      }

int LinkedList::getLength(){
    Node *tempNode=head;
    int count=1;
    if(NULL==head){
                   return 0;
                   }else{

     while(NULL!=tempNode->getNext()){
                   tempNode=tempNode->getNext();
                   count++; 

    }

    return count;
}


}     


LinkedList::LinkedList(){
                         head=NULL;
                        // if(NULL==head){

                          //              head=createNode();
                            //            }

                               }
void LinkedList::addNodeAtTheBeginning(){


             Node *tempNode;
             tempNode=createNode();

             if(NULL!=head){
             tempNode->setNext(head);
             head=tempNode;      
             }else{
                   head=tempNode;                      

              }

             }

void LinkedList::addNodeAtAGivenLocation(int position){

             Node *tempNode;

             Node *tempNode2;

             if(getLength()<position){
                  std::cout<<"No node can be inserted at this poition "<<std::endl;
             }else{
                   tempNode=createNode();   
                     tempNode2=head;             
             for(int i=1;i<position;i++){    

               tempNode2=tempNode2->getNext();  
               }        
                  tempNode->setNext(tempNode2->getNext());
                  tempNode2->setNext(tempNode);                                     
              }



}
void LinkedList::addNodeAtTheEnd(){

                if(NULL==head){
                               head=createNode();
                               }else{
                                 Node *tempNode=head;
                                 while(NULL!=tempNode->getNext()){    
                                     tempNode=tempNode->getNext();
                                     }    
                                     tempNode->setNext(createNode());                
                                    }

}

void LinkedList::deleteFirstNode(){

     Node *tempNode;

     if(NULL==head){
                    std::cout<<"No node available for deletion"<<std::endl;
     }else{

            tempNode=head;
            head=head->getNext();
            delete tempNode;              

                          }

                                    }
void LinkedList::deleteNodeAtAGivenLocation(int position){

             Node *tempNode;

             if(getLength()<=position){
                  std::cout<<"No node can be deleted as no node exist at this poition "<<std::endl;
             }else{

             for(int i=1;i<position;i++){    
               tempNode=head;
               tempNode=tempNode->getNext();  
               }        

                  tempNode->setNext(tempNode->getNext()->getNext()); 
                  delete tempNode->getNext();                                    
              }



                                               }
void LinkedList::deleteLastNode(){

     Node *tempNode;
     Node *tempNode2;

     if(NULL==head){
                    std::cout<<"No node available for deletion"<<std::endl;
     }else{

            tempNode=head;

            while(NULL!=tempNode->getNext()){

            tempNode=tempNode->getNext();
            tempNode2=tempNode;

            }
            tempNode=tempNode->getNext();
            tempNode2->setNext(NULL);
            delete tempNode;              

                          }

                                   }

LinkedList::~LinkedList(){

                         Node *tempNode=NULL;

                         if(NULL==head){
                               std::cout<<"No nodes in the Linked List available for Deletion"<<std::endl;          
                                        }else{

                                              tempNode =head;

                                              while(NULL!=head->getNext()){
                                                                              tempNode=head;
                                                                               head=head->getNext();
                                                                                delete tempNode;
                                                                               }
                                                                               delete head;
                                              }



                         std::cout<<"Linked List Deleted"<<std::endl; 
                         head=NULL;      
                                }

void LinkedList::display(void){

  Node *tempNode;
  tempNode=head;

  if(NULL==head){

        std::cout<<"head-->X";

       }else{

        std::cout<<"head-->";
        while(NULL!=tempNode->getNext()){

                std::cout<<"["<<tempNode->getData()<<"]-->"; 
                tempNode=tempNode->getNext();         

        }
        std::cout<<"["<<tempNode->getData()<<"]-->X"<<std::endl; 

        }

      }

void LinkedList::deleteLinkedList(){

     delete this;
     head=NULL;

     }


char LinkedList::getUserData(){
     char data;
     std::cout<<"Enter Data"<<std::endl;
     std::cin>>data;
     return data;
     }

And Finally the main.cpp

#include <cstdlib>
#include <iostream>
#include"LinkedList.h"
#include"Node.h"
#include<stdlib.h>

void printMenu();
int getUserSelection();
void performOperation(int);
LinkedList lk;


int main(){
    int option=0;
    while(9!=option){
    printMenu();
    option=getUserSelection();
    performOperation(option);

   }


}


void printMenu(void){

                  std::cout<< ""<<std::endl;
                  std::cout<< "1) Add Node At The Beginning"<<std::endl;
                  std::cout<< "2) Add Node At A Given Location"<<std::endl;
                  std::cout<< "3) Add Node At The End"<<std::endl; 
                  std::cout<< "4) Delete First Node"<<std::endl;
                  std::cout<< "5) Delete Node At A Given Location"<<std::endl;
                  std::cout<< "6) Delete Last Node"<<std::endl; 
                  std::cout<< "7) Display "<<std::endl;
                  std::cout<< "8) Delete LinkedList"<<std::endl;
                  std::cout<< "9) Exit"<<std::endl;

            }

int getUserSelection(){
    int option=0;
    std::cout<<"Select an option: "<<std::endl;
    std::cin>>option;
    return option;

}
void performOperation(int option){

          switch (option){
                 case 1:
                      lk.addNodeAtTheBeginning();
                      break;
                 case 2:{
                      int location=0;
                      std::cout<<"Enter a location:"<<std::endl;
                      std::cin>>location;
                       lk.addNodeAtAGivenLocation(location);
                       }
                      break;
                 case 3:
                      lk.addNodeAtTheEnd();
                      break;
                 case 4:
                      lk. deleteFirstNode();
                      break;
                 case 5:{
                      int location=0;
                      std::cout<<"Enter a location:"<<std::endl;
                      std::cin>>location;
                      lk.deleteNodeAtAGivenLocation(location);
                      }
                      break;
                 case 6:
                      lk.deleteLastNode();
                      break;
                 case 7:
                      lk.display();
                      break;

                 case 8:
                      lk.deleteLinkedList();
                      break;                            

                 case 9:
                      exit(0);



          }            
                      }
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