Modify the NumberedList class we implementd during the lecture by adding a member function: void NumberedList::insertPosition(int num, int pos) for inserting a new item at a specified position. A position of 0 means that the value will become the first item on the list, a position of 1 means that the value will become the second item on the list, and so on. A position equal to or greater than the length of the list means that the value is placed at the end of the list.

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Explanation:

#include<iostream>

using namespace std;

class LinkedList

{

private:

   // Declare a structure for the list.

   struct ListNode

   {

   int value;        // The value in this node.

   struct ListNode *next;// To point to the next node.

   };

   ListNode *head;        // List head pointer.

public:

   // Constructor.

   LinkedList()

       { head = NULL; }

   // Destructor

   ~LinkedList();

   // Linked list operations.

   void appendNode( int );

   void insertNode( int );

   void insertNodeAt(int,int);

    void deleteNode( int );

   void Reverse();

   void deleteAt(int);

   int Search(int);

   void display() const;

};

// appendNode appends a node containing the      

// value passed into num, to the end of the list.  

void LinkedList::appendNode( int num )

{

  ListNode *newNode; // To point to a new node.

  ListNode *nodePtr; // To move through the list.

  // Allocate a new node and store num there.

  newNode = new ListNode;

  newNode->value = num;

  newNode->next = NULL;

  // If there are no nodes in the list.

  // make newNode the first node.

  if ( !head )

     head = newNode;

  else // Otherwise, insert newNode at end.

  {

     // Initialize nodePtr to head of list.

     nodePtr = head;

     // Find the last node in the list.

     while ( nodePtr->next )

        nodePtr = nodePtr->next;

     // Insert newNode as the last node.

     nodePtr->next = newNode;

  }    //    end else-if

  display();  

}    //    end function appendNode

// displayList shows the value stored in each              

// node of the linked list pointed to by head.      

void LinkedList::display() const

{

   ListNode *nodePtr; // To move through the list

   if ( !head )

   {

       cout << "\n\tThe list is empty.";

       return;

   }

   // Position nodePtr at the head of the list.

   nodePtr = head;

   cout << "\n\n\tThe elements in the list are:\n\t";

   // While nodePtr points to a node, traverse the list.

    while (nodePtr)

   {

       // Display the value in this node.

       cout << nodePtr->value << " -> ";

       // Move to the next node.

       nodePtr = nodePtr->next;

   }    //    end while.

   cout << "Null";

}    //    end function displayList.

// Reverse function re-arranges node in the list.

void LinkedList::Reverse()

{

   ListNode *nodePtr;

   ListNode *next;

   ListNode *result=NULL;

   if ( !head )

   {

       cout << "\n\tThe list is empty.";

       return;

   }

   // Position nodePtr at the head of the list.

   nodePtr = head;

   while (nodePtr!=NULL)

   {

       next=nodePtr->next;

       nodePtr->next=result;

       result=nodePtr;

       nodePtr=next;

   }

   head=result;

display();

}

// The insertNode function inserts a node with num copied to its value member.                

void LinkedList::insertNode( int num )

{

   ListNode *newNode;             // A new node.

   ListNode *nodePtr;             // To traverse the list.

   ListNode *previousNode = NULL; // The previous node.

   // Allocate a new node and store num there.

   newNode = new ListNode;

   newNode->value = num;

   newNode->next = NULL;

   // If there are no nodes in the list make newNode the first node.

   if ( !head )

       head = newNode;

   else // Otherwise, insert newNode.

   {

       // Position nodePtr at the head of list.

       nodePtr = head;

       //    Initialize previousNode to NULL.

       previousNode = NULL;

       //    Skip all nodes whose value is less than num.

       while ( nodePtr != NULL && nodePtr->value < num )

       {

           previousNode = nodePtr;

           nodePtr = nodePtr->next;

       }

       //If the new node is to be the 1st in the list,

       //    insert it before all other nodes.

       if ( previousNode == NULL )

       {

           head = newNode;

           newNode->next = nodePtr;

       }

       else // Otherwise insert after the previous node.

       {

           previousNode->next = newNode;

           newNode->next = nodePtr;

       }

   }    //    end else-if

display();  

}    //    end function insertNode.

// The insertNode function inserts a node at pos  

//with num copied to its value member.          

void LinkedList::insertNodeAt( int num ,int pos)

{

   ListNode *newNode;             // A new node.

   ListNode *nodePtr;             // To traverse the list.

   ListNode *previousNode = NULL; // The previous node.

   int i=0;

   // Allocate a new node and store num there.

   newNode = new ListNode;

   newNode->value = num;

   newNode->next = NULL;

   // Position nodePtr at the head of list.

       nodePtr = head;

   if(pos==0)//to inserted at first.

   {  

       newNode->next=head;

       head=newNode;

   }

   else

   {

   while(nodePtr != NULL && i<pos) //loop to reach position.

       {  

           previousNode=nodePtr;

           nodePtr=nodePtr->next;

           i++;

       }

       if(nodePtr==NULL)//position not found.

           cout<<"Invalid Position :"<<endl;

       else//inserts node.

       {

           newNode->next=nodePtr;

           previousNode->next=newNode;

       }

   }

   display();

}

//    The deleteNode function searches for a node with num as its value.  

//The node, if found, is deleted from the list and from memory.

void LinkedList::deleteNode( int num )

{

   ListNode *nodePtr;       // To traverse the list.

   ListNode *previousNode;//To point to the previous node.

   // If the list is empty, do nothing.

   if ( !head )

   {

       cout << "\n\tFailed to delete as list is empty.";  

       return;

   }

   // Determine if the first node is the one.

   if ( head->value == num )

   {

       nodePtr = head->next;

       delete head;

       head = nodePtr;

   }

   else

   {

       // Initialize nodePtr to head of list.

       nodePtr = head;

       // Skip all nodes whose value member is not equal to num.

       while (nodePtr != NULL && nodePtr->value != num)

       {

           previousNode = nodePtr;

           nodePtr = nodePtr->next;

       }

building and maintaining the topology is difficult and time consuming. the chance of redundant connections is high, which adds to the high costs and potential for reduced efficiency.

explanation: