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#1 purplesmiles  Icon User is offline

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Splitting linked lists

Posted 09 October 2012 - 10:14 PM

#include <iostream>
#include "C:\Documents and Settings\Administrator\Desktop\hw3_files\Ch5_ProgExercise4\linkedList.h"

using namespace std;

int main()
{
	linkedListType<int> list, subList;
	linkedListType<int> temp, otherList;


	int num;

	cout<<"Enter numbers ending with -999"<<endl;
	cin>>num;

	while(num != -999)
	{
		list.insertLast(num);
		cin>>num;
	}

	temp = list;

	cout<<endl;

	cout<<"list: "<<list<<endl;
	cout<<"Length of the list: "<<list.length()<<endl;

	list.divideMid(subList);

	cout<<"Lists after splitting list"<<endl;

	cout<<"list: "<<list<<endl;
	cout<<"Length of the list: "<<list.length()<<endl;

	cout<<"sublist: "<<subList<<endl;;
	cout<<"Length of subList: "<<subList.length()<<endl;

	return 0;
}





#ifndef H_LinkedListType
#define H_LinkedListType

#include <iostream>
#include <cassert>
using namespace std;

template <class Type>
struct nodeType
{
	Type info;
	nodeType<Type> *link;
};

template<class Type>
class linkedListType
{

    friend ostream& operator<< <Type> (ostream&, const linkedListType<Type>&);

public:
    const linkedListType<Type>& operator=
          			      (const linkedListType<Type>&);
		//Overload the assignment operator.
    void initializeList();
 		//Initializes the list to an empty state.
	    //Postcondition: first = NULL, last = NULL,
		//                count = 0
    bool isEmptyList();
 		//Function to determine whether the list is empty.
		//Postcondition: Returns true if the list is empty;
		//               otherwise, returns false.

	int length();
		//Function to return the number of nodes in the
		//list.
		//Postcondition: The value of count is returned.
    void destroyList();
 		//Function to delete all the nodes from the list.
  		//Postcondition: first = NULL, last = NULL,
		//               count = 0
    Type front();
 		//Function to return the first element of the list.
 		//Precondition: The list must exist and must not be
		//empty.
  		//Postcondition: If the list is empty, then the
 		//               program terminates; otherwise,
	    //               the first element of the list is
		//               returned.
    Type back();
       //Function to return the last element of the
       //list.
		//Precondition: The list must exist and must not
		//be empty.
		//Postcondition: If the list is empty, then the
		//               program terminates; otherwise,
		//               the last element of the list is
		//               returned.

   bool search(const Type& searchItem);
		//Function to determine whether searchItem is in
		//the list.
		//Postcondition: Returns true if searchItem is found
		//               in the list; otherwise, it returns
		//               false.

    void insertFirst(const Type& newItem);
		//Function to insert newItem in the list.
		//Postcondition: first points to the new list
		//                and newItem is inserted at the
		//                beginning of the list.

    void insertLast(const Type& newItem);
		//Function to return newItem at the end of the
		//list.
	    //Postcondition: first points to the new list,
		//                newItem is inserted at the end
		//                of the list, and last points to
		//                the last node in the list.

    void deleteNode(const Type& deleteItem);
  		//Function to delete deleteItem from the list.
 		//Postcondition: If found, the node containing
   		//               deleteItem is deleted from the
		//                list, first points to the first
		//                node, and last points to the last
		//                node of the updated list.


	void divideMid(linkedListType<Type> &sublist);
	   //This operation splits the given list in two sublists of
       //(almost) equal size.
       //Post: first points the first node and last
       //       points to the last node of the first sublist
       //       sublist.first points to the first node and sublist.last
       //       points to the last node of the second sub list.


    linkedListType();
   		//default constructor
 		//Initializes the list to an empty state.
 		//Postcondition: first = NULL, last = NULL,
		//               count = 0

    linkedListType(const linkedListType<Type>& otherList);
         //copy constructor

    ~linkedListType();
    	//destructor
   		//Deletes all the nodes from the list.
    	//Postcondition: The list object is destroyed.

protected:
    int count;		//variable to store the number of
 					//elements in the list
    nodeType<Type> *first; //pointer to the first node of
                           //the list
    nodeType<Type> *last;  //pointer to the last node of
                           //the list
private:
    void copyList(const linkedListType<Type>& otherList);
		//Function to make a copy of otherList.
		//Postcondition: A copy of otherList is created
		//               and assigned to this list.
};

template<class Type>
bool linkedListType<Type>::isEmptyList()
{
	return(first == NULL);
}

template<class Type>
linkedListType<Type>::linkedListType() // default constructor
{
	first = NULL;
	last = NULL;
	count = 0;
}

template<class Type>
void linkedListType<Type>::destroyList()
{
	nodeType<Type> *temp;   //pointer to deallocate the memory
							//occupied by the node
	while(first != NULL)    //while there are nodes in the list
	{
	   temp = first;        //set temp to the current node
	   first = first->link; //advance first to the next node
	   delete temp;         //deallocate memory occupied by temp
	}

	last = NULL;	//initialize last to NULL; first has already
                   //been set to NULL by the while loop
 	count = 0;
}


template<class Type>
void linkedListType<Type>::initializeList()
{
	destroyList(); //if the list has any nodes, delete them
}

template<class Type>
int linkedListType<Type>::length()
{
 	return count;
}  // end length

template<class Type>
Type linkedListType<Type>::front()
{
    assert(first != NULL);
   	return first->info; //return the info of the first node
}//end front


template<class Type>
Type linkedListType<Type>::back()
{
	 assert(last != NULL);
   	 return last->info; //return the info of the first node
}//end back

template<class Type>
bool linkedListType<Type>::search(const Type& searchItem)
{
    nodeType<Type> *current; //pointer to traverse the list
    bool found;

    current = first; //set current to point to the
                     //first node in the list
    found = false;   //set found to false

    while(current != NULL && !found)		//search the list
        if(current->info == searchItem)     //item is found
           found = true;
        else
           current = current->link; //make current point
                                    //to the next node

     return found;
}//end search

template<class Type>
void linkedListType<Type>::insertFirst(const Type& newItem)
{
	nodeType<Type> *newNode; //pointer to create the new node

	newNode = new nodeType<Type>; //create the new node

	assert(newNode != NULL);	//If unable to allocate memory,
 								//terminate the program

	newNode->info = newItem; 	   //store the new item in the node
	newNode->link = first;        //insert newNode before first
	first = newNode;              //make first point to the
                                 //actual first node
	count++; 			   //increment count

	if(last == NULL)   //if the list was empty, newNode is also
                      //the last node in the list
		last = newNode;
}

template<class Type>
void linkedListType<Type>::insertLast(const Type& newItem)
{
	nodeType<Type> *newNode; //pointer to create the new node

	newNode = new nodeType<Type>; //create the new node

	assert(newNode != NULL);	//If unable to allocate memory,
 							//terminate the program

	newNode->info = newItem;      //store the new item in the node
	newNode->link = NULL;         //set the link field of newNode
         						//to NULL

	if(first == NULL)	//if the list is empty, newNode is
     					//both the first and last node
	{
		first = newNode;
		last = newNode;
		count++;		//increment count
	}
	else			//the list is not empty, insert newNode after last
	{
		last->link = newNode; //insert newNode after last
		last = newNode;   //make last point to the actual last node
		count++;		//increment count
	}
}//end insertLast

template<class Type>
void linkedListType<Type>::deleteNode(const Type& deleteItem)
{
	nodeType<Type> *current; //pointer to traverse the list
	nodeType<Type> *trailCurrent; //pointer just before current
	bool found;

	if(first == NULL)    //Case 1; list is empty.
		cerr<<"Can not delete from an empty list.\n";
	else
	{
		if(first->info == deleteItem) //Case 2
		{
			current = first;
			first = first->link;
			count--;
			if(first == NULL)    //list had only one node
				last = NULL;
			delete current;
		}
		else  //search the list for the node with the given info
		{
			found = false;
			trailCurrent = first;   //set trailCurrent to point to
                                 //the first node
			current = first->link;  //set current to point to the
    			   //second node

			while((!found) && (current != NULL))
			{
  				if(current->info != deleteItem)
				{
					trailCurrent = current;
					current = current-> link;
				}
				else
					found = true;
			} // end while

			if(found) //Case 3; if found, delete the node
			{
				trailCurrent->link = current->link;
				count--;

				if(last == current)      //node to be deleted was
                                     //the last node
					last = trailCurrent;  //update the value of last
				delete current;  //delete the node from the list
			}
			else
				cout<<"Item to be deleted is not in the list."<<endl;
		} //end else
	} //end else
} //end deleteNode


	//Overloading the stream insertion operator
template<class Type>
ostream& operator<<(ostream& osObject, const linkedListType<Type>& list)
{
	nodeType<Type> *current; //pointer to traverse the list

	current = list.first;   //set current so that it points to
					   //the first node
	while(current != NULL) //while more data to print
	{
	   osObject<<current->info<<" ";
	   current = current->link;
	}

	return osObject;
}

template<class Type>
linkedListType<Type>::~linkedListType() // destructor
{
	destroyList();
}//end destructor


template<class Type>
void linkedListType<Type>::copyList
            	      (const linkedListType<Type>& otherList)
{
   nodeType<Type> *newNode; //pointer to create a node
   nodeType<Type> *current; //pointer to traverse the list

   if(first != NULL)	//if list is nonempty, make it empty
	  destroyList();

   if(otherList.first == NULL) //otherList is empty
   {
		first = NULL;
		last = NULL;
 		count = 0;
   }
   else
   {
		current = otherList.first;  //current points to the
									//list to be copied
		count = otherList.count;

			//copy the first node
		first = new nodeType<Type>;  //create the node

 		assert(first != NULL);

		first->info = current->info; //copy the info
		first->link = NULL;  	     //set the link field of
									 //the node to NULL
		last = first;    		     //make last point to the
            						 //first node
		current = current->link;     //make current point to the
           							 //next node

			//copy the remaining list
		while(current != NULL)
		{
			newNode = new nodeType<Type>;  //create a node

			assert(newNode!= NULL);

			newNode->info = current->info;	//copy the info
			newNode->link = NULL;   	    //set the link of
                                        //newNode to NULL
			last->link = newNode; 		//attach newNode after last
			last = newNode;   			//make last point to
										//the actual last node
			current = current->link;	//make current point to
       									//the next node
		}//end while
	}//end else
}//end copyList


	//copy constructor
template<class Type>
linkedListType<Type>::linkedListType
            	      (const linkedListType<Type>& otherList)
{
	first = NULL;

	copyList(otherList);

}//end copy constructor

	//overload the assignment operator
template<class Type>
const linkedListType<Type>& linkedListType<Type>::operator=
   	 	 		(const linkedListType<Type>& otherList)
{

	if(this != &otherList) //avoid self-copy
	{
		copyList(otherList);
	}//end else

	return *this;
}

template<class Type>
void linkedListType<Type>::divideMid(linkedListType<Type> &sublist)
{
    nodeType<Type> *current;
	nodeType<Type> *mid;

	if (first == NULL)
	{

		sublist.first = NULL;
		sublist.last = NULL;
	}
	else
		if (first->link == NULL)
		{
			sublist.first = NULL;
			sublist.last = NULL;
		}
		else
		{
			mid = first;
			current = first->link;

			if (current != NULL)
				current = current->link;

			while (current != NULL)
			{
				mid = mid->link;
				current = current->link;

				if (current != NULL)
					current = current->link;
			}

			sublist.first = mid->link;
			sublist.last = last;
			last = mid;
			last->link = NULL;
		}
}

#endif





Here is the problem. I'm given the code for everything but the divideMid() function. That part, I was supposed to write. I've written that part of the code. However, the program will not compile. There are several errors that show up that are mainly attached to the
friend ostream& operator<< <Type> (ostream&, const linkedListType<Type>&);
and this error also occurs: error: `nodeType<int>*linkedListType<int>::first' is protected|

I believe that all of these errors were there before I input my part of the coding. I'm not supposed to alter the rest of the program but I can't check my part of the program until these errors are fixed. Any help is greatly appreciated.

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Replies To: Splitting linked lists

#2 jimblumberg  Icon User is offline

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Re: Splitting linked lists

Posted 09 October 2012 - 11:09 PM

Yes there is a problem with the friend declaration in your class. If you change it to:
   template <typename MyType>
   friend ostream& operator<< (ostream&, const linkedListType<Type>&);



Your program should compile, for this problem. See this link for an explanation of this problem: Template friend function of a template class.

Jim

This post has been edited by jimblumberg: 09 October 2012 - 11:25 PM

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#3 baavgai  Icon User is offline

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Re: Splitting linked lists

Posted 10 October 2012 - 04:29 AM

I'd define your nodeType in your linkedListType and give it a constructor.

Also, you don't need a friend, just a method. Avoid friends when you can. e.g.
template<typename T>
void linkedListType<T>::print(std::ostream &out) const {
	for(nodeType<Type> *p = first; p != NULL; p = p->link) {
		out << p->info << ' ';
	}
}

// no friend needed, there is a public const method than can be called
template<typename T>
std::ostream& operator<<(std::ostream &out, const linkedListType<T> &list) {
	list.print(out);
	return out;
}


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