Anyone good with linked list.....I am not....

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  1. #1
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    Anyone good with linked list.....I am not....

    So I decided it was time for me to learn linked list and boy oh boy I never thought I would be in for such a treat. In order to do this I have been following through a chapter in a book and trying to fill in things as I go along. I have made it pretty fat and am grasping a lot of things but there is still one major problem I am having. Funny thing is it mostly does not have to do with Linked List themselevs. Anyways I am trying to write two functions one to display the n'th node in a list and another to delete the n'th node in the list (n'th being a number the user inputs). So for example say the user wants to delete the 9th node in the list. The function will traverse the list until it reaches the 9th node and delete it. I think I have to use a for loop and then set a pointer to the current node but I am just not sure.

    WARNING********

    I am posting a hefty amount of code. I have commented out the two functions I am still trying to figure out with three lines worth of //////. The only reason why I am posting so much code is because I feel like the it is essential to anyone who is willing to help me. If it is not please let me know so I can shorten it.

    Warning**********

    Anyways if anyone would like to have a stab at it or and let me know what your thoughts are that would be great.

    If there is anyway I can make this mor legiable let me know...

    Code:
    using#ifndef H_LinkedListType
    #define H_LinkedListType
    #include "stdafx.h"
    #using <mscorlib.dll>
    #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<<(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. 
    //////////////////////////////////////////////////////////////////
    ///////////////////////////////H E L P ///////////////////////////
    //////////////////////////////////////////////////////////////////
    	Type getKThElement(int k); 
    		//Function to search list for the n'th node in the list
    		//Postcondition: When found display info
    	
    	void deteteKthElement(int k);
    		//Function used to delete the n'th number node in the 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
    /////////////////////////////////////////////////////////////////
    /////////////////////////////H E L P/////////////////////////////
    /////////////////////////////////////////////////////////////////
    template<class Type>
    Type getKThElement(int k)
    {
    // User enters a number 
    // Traverse list until you have reached users number (for loop?)
    // Display result
    }
    /////////////////////////////////////////////////////////////////
    /////////////////////////////////////////////////////////////////
    /////////////////////////////////////////////////////////////////
    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
    ////////////////////////////////////////////////////////////////////
    /////////////////////////////////H E L P////////////////////////////
    ////////////////////////////////////////////////////////////////////
    void deteteKthElement(int k)
    {
    //User enters number
    //Traverse list until you reach that node
    //Delete node
    }
    ////////////////////////////////////////////////////////////////////
    ////////////////////////////////////////////////////////////////////
    ////////////////////////////////////////////////////////////////////
    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; 
    }
    
    int _tmain()
    {
    	return 0;
    }

    Thanks

    Chad

  2. #2
    Frequently Quite Prolix dwks's Avatar
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    Code:
    template<class Type>
    linkedListType<Type>::linkedListType() // default constructor
    {
    	first = NULL;
    	last = NULL;
    	count = 0;
    }
    could initialize the variables in the initialization list.

    Does that compile? Did you write it? It seems to me that
    Code:
    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;
    some of those values are protected.

    Code:
    int _tmain()
    {
    	return 0;
    }
    Ugh.
    dwk

    Seek and ye shall find. quaere et invenies.

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  3. #3
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    Quote Originally Posted by dwks
    Code:
    template<class Type>
    linkedListType<Type>::linkedListType() // default constructor
    {
    	first = NULL;
    	last = NULL;
    	count = 0;
    }
    could initialize the variables in the initialization list.
    Dully noted, I will do that......

    Does that compile? Did you write it? It seems to me that
    Code:
    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;
    some of those values are protected.
    Yup, complies fine.....Me and a freind who have been trying to learn linked list have been shooting this back and forth to each other....


    Code:
    int _tmain()
    {
    	return 0;
    }
    Ugh.
    hahah don't pay attention to that...I should have taken it out....

  4. #4
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    Last (bump) attempt at getting help for this topic.....

    Thanks

    Chad

  5. #5
    &TH of undefined behavior Fordy's Avatar
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    Bump this thread again, and I'll close it.

    http://cboard.cprogramming.com/annou...ouncementid=51

  6. #6
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    Quote Originally Posted by Fordy
    Bump this thread again, and I'll close it.

    http://cboard.cprogramming.com/annou...ouncementid=51
    Sorry...I missed that...

  7. #7
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    Hi,

    Conceptually it's not very difficult to remove the nth node. Try writing it as a non-templated function first.

    1) Get a pointer to the first node: Node* target = getStart();
    2) Start counting: i = 0;
    3) Advance the pointer to the next node: target = target.getNext();
    4) Increment the counter: ++i;
    5) When the counter equals n, the loop should end. When the loop ends, target will point to the node you want to remove.
    6) Get the nodeBefore using the target node's previous pointer.
    7) Get the nodeAfter using the target node's next pointer.
    8) First handle the reassignment of nodeBefore's next pointer. Do some checking to see if nodeBefore is 0, which means target is the first node. If nodeBefore is zero, then it has no next pointer pointing to target, and no reassignment is necessary. However, in that case removing target changes first, so get first and assign nodeAfter to it. If nodeBefore isn't zero, get its next pointer and assign nodeAfter to it, so you have:
    nodeBefore--->nodeAfter.
    9) Do some checking to see if the nodeAfter is 0, which means the target is the last node. If nodeAfter is zero, then it has no previous pointer pointing to target, and no reassignment is necessary. However, in that case removing target changes last, so get last and assign nodeBefore to it. If nodeAfter isn't zero, get its previous pointer and assign nodeBefore to it, so you have:
    nodeBefore <-------- nodeAfter.
    10) Lean back and sip on a cold beer as you admire your handywork.

    Bloody hell. That was for a doubly linked list, which allows forward and backward movement. But, singly linked lists are even easier.
    Last edited by 7stud; 11-09-2005 at 01:05 AM.

  8. #8
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    I have to pay more attention I should have just updated this post instead of posting a new one..

    Sorry

    Chad
    Last edited by chadsxe; 11-09-2005 at 01:27 PM.

  9. #9
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    I am not at step 10 yet but I feel like I am on the correct path....How does this look for a start

    Code:
    	nodeType *current = first->link;
    	nodeType *trail = first;
        
    	for (int i = 0; i < pos; i++)
    	{
    		current = current->link;
    		trail = trail->link;
    	}
    	
    	if (first == NULL)
    	{
    		cout << "List is Empty" << endl;
    	}
    	else 
    	{
    		if (current->link != NULL)
    		{
    			trail = current->link;
    			delete current;
    		}
    		else (current->info == NULL)
    		{
    			trail->link = NULL;
    			delete current;
    		}
    	}
    Thanks

    Chad

  10. #10
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    1) Don't use NULL. "Real" C++ programmers use 0.

    2)
    Code:
    nodeType *current = first->link;
    nodeType *trail = first;
    
    for (int i = 0; i < pos; i++)
    {
    	current = current->link;
    	trail = trail->link;
    }
    That's a little confusing for me. You have a pointer to the first node(trail) and a pointer to the second node(current), and you are advancing them along the list. If pos is 2, then your for-loop will end after two loops, and you'll have a pointer to the 3rd element(trail) and a pointer to the 4th element(current). What's the point of advancing two pointers along the list? In addition, you need pointers to three nodes to remove a node: a pointer to the node before the node you want to remove, a pointer to the node you want to remove, and pointer to the node after the node you want to remove.

    3) Why perform any calculations and declare variables prior to checking if the list is empty?
    Code:
    if (first == NULL)
    {
    	cout << "List is Empty" << endl;
    }
    4)
    Code:
    if (current->link != NULL)
    current is already several nodes after the node you want to remove(see #1). Hence, current->link is even further down the list, and therefore is irrelevant. Well, not completely irrelevant because if you use the -> operator, that is equivalent to calling the dereference(*) operator and then the member access operator(.), which means you'll be dereferencing a null pointer if you are at the end of the list, and as a result your program will crash. Actually, your program can crash even earlier. What happens if the list has 3 nodes and you try to remove node 10? As you step through the list in your for-loop using ->, you will hit the end up of the list at some point(current will get there first), which means current will be equal to 0, and on the next loop dereferencing current using -> will cause your program to crash.

    When you step through a linked list, there has to be a loop conditional that checks whether you have reached the end of the list.
    Last edited by 7stud; 11-09-2005 at 02:28 PM.

  11. #11
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    Well hear is the progress I am making.....I removed all the templating I had for the sake of working things out....I also removed a couple of functions and am now trying to get the ones I am most concerned about working......as of now everything compiles but I am having a hard time checking my work....this is do to the fact that I don't think I have built my displayFuntion method correctly........also when I do search for a node it ends up crashing......anyone have any ideas......if you need more info let me know...

    Thanks

    Chad

    Code:
    using#ifndef H_LinkedListType
    #define H_LinkedListType
    #include "stdafx.h"
    #include <string>
    #include <fstream>
    #include <iostream>
    #include <cassert>
    using namespace std;
    
    struct nodeType
    {
    	string info;
    	nodeType *link;
    };
    
    class linkedListType
    {
    	friend ostream& operator<<(ostream&, const linkedListType&);
    
    public:
        const linkedListType& operator=(const linkedListType&); 
        void initializeList(); 
        bool isEmptyList();
        int length();
        void destroyList();
        void insertFirst(string name);
        void insertLast(string name);
    
    ///////////////////////////////H E L P ///////////////////////////
    	void getKThElement(int pos); 
    	void linkedListType::Display_List();
    	void deteteKthElement(int pos);
    //////////////////////////////////////////////////////////////////
    
        linkedListType(); 
        ~linkedListType();   
     
    protected:
        int count;		
        nodeType *first; 
        nodeType *last;  
    };
    
    bool linkedListType::isEmptyList()
    {
    	return(first == NULL);
    }
    
    linkedListType::linkedListType()// default constructor
    {
    	first = NULL;
    	last = NULL;
    	count = 0;
    }
    
    void linkedListType::destroyList()
    {
    	nodeType *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;
    }
    
    void linkedListType::initializeList()
    {
    	destroyList(); //if the list has any nodes, delete them
    }
    
    int linkedListType::length()
    {
     	return count;
    }  // end length
    
    ////////////////////////////Help//////////////////////////////
    void linkedListType::Display_List()
    {  
    	nodeType *temp;
    	last = NULL;
        temp = first;
    	
         
    	cout << endl;
        if (first == NULL)
    	cout << "The list is empty!" << endl;
        else
    		{ 
    			while (temp != NULL)
    			{  
    			// Display details for what temp points to
    			cout << "Name: " << temp->info << flush;
    		//	if (temp == current)
    		//	cout << " <-- Current node";
    		//	cout << endl;
    			temp = temp->link;
    	   }
    	 cout << "End of list!" << endl;
         }
      }
    /////////////////////////////H E L P///////////////////////////
    void linkedListType::getKThElement(int pos)
    {   
    	nodeType *current = first->link;
    	nodeType *trail = first;
    	bool found;
    	int count = 0;
        
    	if (first == NULL)//First check if the list is empty....
    	{
    		cout << "The list is Empty!" << endl;
    	}
    	else
    	{
    		if (pos == count && pos == NULL)//Then check to see if pos is the last
    		{								//node
    			current = first; //set current to the first node
    			first = first->link; //set first to the second node
    			count--;//update count
    			if(first == NULL)    //list had only one node
    				last = NULL; //set last to NULL(0)
    			delete current; //delete the current node
    		}
    		else
    		{
    			found = false;
    			current = first->link;  //set current to point to the 
        
    			//Search for node
    			while((!found) && (current != NULL))//While found is false && current is 
    			{									//not the last node 
      				    count++;  //get the total number of nodes
    					current = current-> link; //advance through the list
    			} 
    
    			if(count >= pos) //Check to see if pos is found 
    			{
    				found = true; //if so its there
    			}
    			else
    			{
    				cout<<"Count > than pos";
    			//	return 0;
    			}
    
    			if(found) //if found then delete the node
    			{
    				current=first;
    				for(count=0; count != pos; count++)
    				{
    					trail=current;
    					current = current-> link;
    				}
    				if(last == current)      //node to be deleted was 
                                         //the last node
    					last = trail;  //Another special case update the value of last
    				else
    				{
    					trail->link = current->link;
    				}					
    				cout << "You just found: " << current->info << endl;  
    			}
    			else
    				cout<<"Item to be found is not in the list."<<endl;
    		}
    	} 
    }
    /////////////////////////////////////////////////////////////////
    
    void linkedListType::insertFirst(string name)
    {
    	nodeType *newNode; //pointer to create the new node
    
    	newNode = new nodeType; //create the new node
    
    	assert(newNode != NULL);	//If unable to allocate memory, 
     								//terminate the program
    
    	newNode->info = name; 	   //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;
    }
    
    /////////////////////////////////H E L P////////////////////////////
    void linkedListType::deteteKthElement(int pos)
    {
    	nodeType *current = first->link;
    	nodeType *trail = first;
    	bool found;
    	int count = 0;
        
    	if (first == NULL)//First check if the list is empty....
    	{
    		cout << "The list is Empty!" << endl;
    	}
    	else
    	{
    		if (pos == count && pos == NULL)//Then check to see if pos is the last
    		{								//node
    			current = first; //set current to the first node
    			first = first->link; //set first to the second node
    			count--;//update count
    			if(first == NULL)    //list had only one node
    				last = NULL; //set last to NULL(0)
    			delete current; //delete the current node
    		}
    		else
    		{
    			found = false;
    			current = first->link;  //set current to point to the 
        
    			//Search for node
    			while((!found) && (current != NULL))//While found is false && current is 
    			{									//not the last node 
      				    count++;  //get the total number of nodes
    					current = current-> link; //advance through the list
    			} 
    
    			if(count >= pos) //Check to see if pos is found 
    			{
    				found = true; //if so its there
    			}
    			else
    			{
    				cout<<"Count > than pos";
    			//	return 0;
    			}
    
    			if(found) //if found then delete the node
    			{
    				current=first;
    				for(count=0; count != pos; count++)
    				{
    					trail=current;
    					current = current-> link;
    				}
    				if(last == current)      //node to be deleted was 
                                         //the last node
    					last = trail;  //Another special case update the value of last
    				else
    				{
    					trail->link = current->link;
    				}
    					
    				delete current;  //delete the node from the list
    
    			}
    			else
    				cout<<"Item to be deleted is not in the list."<<endl;
    		}
    	} 
    }
    ////////////////////////////////////////////////////////////////////
    
    //Overloading the stream insertion operator
    ostream& operator<<(ostream& osObject, const linkedListType& list)
    {
    	nodeType *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;
    }
    
    linkedListType::~linkedListType() // destructor
    {
    	destroyList(); 
    }//end destructor
    
    //overload the assignment operator
    const linkedListType& linkedListType::operator=
       	 	 		(const linkedListType& otherList)
    { 
         
    	if(this != &otherList) //avoid self-copy
    	{
    				///copy list
    	}//end else
    
    	return *this; 
    }
    
    void displayMenu()
    {
    	cout << "Select one of the following:" << endl;
    	cout << "1: To search for a node" << endl;
    	cout << "2: To search and delete a node" << endl;
    	cout << "3: Add Name" << endl;
    	cout << "0: EXIT" << endl;
    }
    
    void controller(int i)
    {
    	string name;
    	int pos;
    	linkedListType link;
    
    			if (i == 1)
    			{
    				cout << "Enter the number of the Node to Search For: ";
    				cin >> pos;
    				link.getKThElement(pos);
    			}
    			else if (i == 2)
    			{
    				cout << "Enter the Name of the Node you want to delete: ";
    				cin >> pos;
    				link.deteteKthElement(pos);
    			}
    			else if (i == 3)
    			{
    				cout << "Add Name: ";
    				cin >> name;
    				link.insertFirst(name);
    			}			
    			else
    			{
    				cout << "Invalid Selection" << endl;
    			}
    }
    
    void GetInput()
    {
    	int i;
    	linkedListType link;
    do
    	{
    		link.Display_List();
    		displayMenu();
    		cout << "Please select a number from below: " << flush;
    		cin >> i;
    		controller(i);
    	}
    	while (i != 0);
    }
    
    int _tmain()
    {
    	GetInput();
    	return 0;
    }

  12. #12
    Registered User
    Join Date
    Apr 2003
    Posts
    2,662
    The proper approach to writing programs is to write one function at a time. After you write your first function, you test it to make sure it works. Then you move onto your next function. A bad approach is to write the whole program and then try to compile it. You'll most likely have a lot of errors, and they will be difficult to track down. After the constructors, the first function you need to write is a funtion to add nodes to the list. The second function you need to write is one that displays the elements in the list. So, at this point, your program should consist of only those two functions.

    In a linked list, you typically don't insert nodes at the beginning; you insert them at the end.
    Last edited by 7stud; 11-10-2005 at 01:57 PM.

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