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Linked List Delete

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Join Date: Dec 2007

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Reputation: henpecked1 is an unknown quantity at this point

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henpecked1 henpecked1 is offline

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Linked List Delete

Aug 21st, 2008

I'm having trouble getting my delete function to work for a singly linked list. If I try to delete anything other than the entire list, it deletes everything up to that node.

I know there is something wrong with it, but I can't tell what it is. I would like to structure it so that it can delete any one node in the list, then I'd like to be able to print the list to the screen. btw, insert and print work fine, just not the delete. Here is the code

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
bool list::del(Contributor Del)
{
	 Contributor infoIn=Del;
 
	node *pprev= plist; 
	node *ptrav= plist; 
 
	if (empty())	//empty list
	     {
		cout<<"The list is empty "<<endl;	
	     }
 
	if (pprev==ptrav)	//list beginning
	     {
 
	                   plist = ptrav->next;	  //sends plist to next node
		   delete ptrav;			  //delete Node
	      }
 
	 while((ptrav!=NULL) && (ptrav->infoIn!=Del))
	      {
		pprev= ptrav;
		ptrav= ptrav->next;
	       }			
 
                  if (pprev==ptrav) 
	                 return false;
                   else
	               if(pprev==NULL)
                                    { 
			plist= plist->next;
			delete ptrav;			
		      }
		else
		      {
			pprev->next =ptrav->next;
			delete ptrav;
		       }
 
	   return true;
}
bool list::del(Contributor Del)
{
	 Contributor infoIn=Del;
	 
	node *pprev= plist; 
	node *ptrav= plist; 

	if (empty())	//empty list
	     {
		cout<<"The list is empty "<<endl;	
	     }

	if (pprev==ptrav)	//list beginning
	     {
				
	                   plist = ptrav->next;	  //sends plist to next node
		   delete ptrav;			  //delete Node
	      }
			
	 while((ptrav!=NULL) && (ptrav->infoIn!=Del))
	      {
		pprev= ptrav;
		ptrav= ptrav->next;
	       }			
	
                  if (pprev==ptrav) 
	                 return false;
                   else
	               if(pprev==NULL)
                                    { 
			plist= plist->next;
			delete ptrav;			
		      }
		else
		      {
			pprev->next =ptrav->next;
			delete ptrav;
		       }

	   return true;
}

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Join Date: Aug 2008

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findsyntax findsyntax is offline

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Re: Linked List Delete

Aug 21st, 2008

Hi,
I am Rammohan from Bangalore and working as a Technical lead in big IT firm .

Solution for your answer is follows:

The way you have written is only for the deleting a node. For that also you have not verified weather the node is exist in the list or not.
Please have a look at my style fo code and use it where ever you want.

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
struct node *DeleteNode ( struct node *p, int node_no )
{
	struct node *prev, *curr ;
	int i;
	if (p == NULL )
	{
		printf("There is no node to be deleted \n");
	}
	else
	{
		if ( node_no > length (p))
		{
			printf("Error\n");
		}
		else
		{
			prev = NULL;
			curr = p;
			i = 1 ;
			while ( i < node_no )
			{
				prev = curr;
				curr = curr-> link;
				i = i+1;
			}
			if ( prev == NULL )
			{
				p = curr -> link;
				free ( curr );
			}
			else
			{
				prev -> link = curr -> link ;
				free ( curr );
			}
		}
	}
	return(p);
}
struct node *DeleteNode ( struct node *p, int node_no )
{
	struct node *prev, *curr ;
	int i;
	if (p == NULL )
	{
		printf("There is no node to be deleted \n");
	}
	else
	{
		if ( node_no > length (p))
		{
			printf("Error\n");
		}
		else
		{
			prev = NULL;
			curr = p;
			i = 1 ;
			while ( i < node_no )
			{
				prev = curr;
				curr = curr-> link;
				i = i+1;
			}
			if ( prev == NULL )
			{
				p = curr -> link;
				free ( curr );
			}
			else
			{
				prev -> link = curr -> link ;
				free ( curr );
			}
		}
	}
	return(p);
}

Regards,
Rammohan Alampally,
<snip false signature>

Last edited by Ancient Dragon; Aug 21st, 2008 at 7:45 am. Reason: snip false signature and add code tags

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Join Date: Jan 2008

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VernonDozier VernonDozier is offline

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Re: Linked List Delete

Aug 21st, 2008

•

Originally Posted by henpecked1

I'm having trouble getting my delete function to work for a singly linked list. If I try to delete anything other than the entire list, it deletes everything up to that node.

I know there is something wrong with it, but I can't tell what it is. I would like to structure it so that it can delete any one node in the list, then I'd like to be able to print the list to the screen. btw, insert and print work fine, just not the delete. Here is the code
Help with Code Tags

C++ Syntax (Toggle Plain Text)
bool list::del(Contributor Del)
{
	 Contributor infoIn=Del;
 
	node *pprev= plist; 
	node *ptrav= plist; 
 
	if (empty())	//empty list
	     {
		cout<<"The list is empty "<<endl;	
	     }
 
	if (pprev==ptrav)	//list beginning
	     {
 
	                   plist = ptrav->next;	  //sends plist to next node
		   delete ptrav;			  //delete Node
	      }
 
	 while((ptrav!=NULL) && (ptrav->infoIn!=Del))
	      {
		pprev= ptrav;
		ptrav= ptrav->next;
	       }			
 
                  if (pprev==ptrav) 
	                 return false;
                   else
	               if(pprev==NULL)
                                    { 
			plist= plist->next;
			delete ptrav;			
		      }
		else
		      {
			pprev->next =ptrav->next;
			delete ptrav;
		       }
 
	   return true;
}
bool list::del(Contributor Del) { Contributor infoIn=Del; node *pprev= plist; node *ptrav= plist; if (empty()) //empty list { cout<<"The list is empty "<<endl; } if (pprev==ptrav) //list beginning { plist = ptrav->next; //sends plist to next node delete ptrav; //delete Node } while((ptrav!=NULL) && (ptrav->infoIn!=Del)) { pprev= ptrav; ptrav= ptrav->next; } if (pprev==ptrav) return false; else if(pprev==NULL) { plist= plist->next; delete ptrav; } else { pprev->next =ptrav->next; delete ptrav; } return true; }

I think you need to post more code or comment the code you have or something. We have no idea what these variables represent and what the classes are.

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henpecked1 henpecked1 is offline

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Re: Linked List Delete

Aug 21st, 2008

I commented, as the other code might prove overly long

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
bool list::del(Contributor Del)
{
	 Contributor infoIn=Del;   //Contributor is the object, infoIn is the specific object
 
	node *pprev= plist;         //plist is the beginning of the list, ptrav is what some
	node *ptrav= plist;          // would call "temp" or "head", and pprev is the "tail"
 
	if (empty())	     // checking for empty list
	     {
		cout<<"The list is empty "<<endl;	
	     }
 
	if (pprev==ptrav)	                             //to delete from beginning of list
	     {
 
	                   plist = ptrav->next;	              //sends plist to next node
		   delete ptrav;                        //delete Node
	      }
 
	 while((ptrav!=NULL) && (ptrav->infoIn!=Del))
	      {
		pprev= ptrav;
		ptrav= ptrav->next;
	       }			             //These functions should search for the
	                                                             // proper item to delete, and delete it
                  if (pprev==ptrav) 
	                 return false;
                   else
	               if(pprev==NULL)
                                    { 
			plist= plist->next;
			delete ptrav;			
		      }
		else
		      {
			pprev->next =ptrav->next;
			delete ptrav;
		       }
 
	   return true;
}
bool list::del(Contributor Del)
{
	 Contributor infoIn=Del;   //Contributor is the object, infoIn is the specific object
	                                      
	node *pprev= plist;         //plist is the beginning of the list, ptrav is what some
	node *ptrav= plist;          // would call "temp" or "head", and pprev is the "tail"

	if (empty())	     // checking for empty list
	     {
		cout<<"The list is empty "<<endl;	
	     }

	if (pprev==ptrav)	                             //to delete from beginning of list
	     {
				
	                   plist = ptrav->next;	              //sends plist to next node
		   delete ptrav;                        //delete Node
	      }
			
	 while((ptrav!=NULL) && (ptrav->infoIn!=Del))
	      {
		pprev= ptrav;
		ptrav= ptrav->next;
	       }			             //These functions should search for the
	                                                             // proper item to delete, and delete it
                  if (pprev==ptrav) 
	                 return false;
                   else
	               if(pprev==NULL)
                                    { 
			plist= plist->next;
			delete ptrav;			
		      }
		else
		      {
			pprev->next =ptrav->next;
			delete ptrav;
		       }

	   return true;
}

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Join Date: Dec 2005

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Salem

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Re: Linked List Delete

Aug 21st, 2008

Sheesh - 200 posts, and the indentation is still crap.

Your super IDE may be able to make sense of your crazy mix of spaces and tabs, but most everything else will (sooner or later) make a complete pig's ear of it.

Do everyone a favour and turn OFF tabs, and turn on smart indenting with spaces. It won't cost you any extra keystrokes, and it'll make for a much better experience all round.

Here, indented with spaces only

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
bool list::del(Contributor Del)
{
    Contributor infoIn=Del;     // Contributor is the object, 
                                // infoIn is the specific object
 
    node *pprev= plist;         // plist is the beginning of the list, 
                                // ptrav is what some
    node *ptrav= plist;         // would call "temp" or "head",
                                // and pprev is the "tail"
 
    if (empty())                // checking for empty list
    {
        cout<<"The list is empty "<<endl;    
    }
 
    if (pprev==ptrav)           //to delete from beginning of list
    {
 
        plist = ptrav->next;    //sends plist to next node
        delete ptrav;           //delete Node
    }
 
    while((ptrav!=NULL) && (ptrav->infoIn!=Del))
    {
        pprev= ptrav;
        ptrav= ptrav->next;
    }                           //These functions should search for the
 
    // proper item to delete, and delete it
    if (pprev==ptrav) 
        return false;
    else
    if(pprev==NULL)
    { 
        plist= plist->next;
        delete ptrav;            
    }
    else
    {
        pprev->next =ptrav->next;
        delete ptrav;
    }
 
    return true;
}
bool list::del(Contributor Del)
{
    Contributor infoIn=Del;     // Contributor is the object, 
                                // infoIn is the specific object
    
    node *pprev= plist;         // plist is the beginning of the list, 
                                // ptrav is what some
    node *ptrav= plist;         // would call "temp" or "head",
                                // and pprev is the "tail"

    if (empty())                // checking for empty list
    {
        cout<<"The list is empty "<<endl;    
    }

    if (pprev==ptrav)           //to delete from beginning of list
    {
        
        plist = ptrav->next;    //sends plist to next node
        delete ptrav;           //delete Node
    }
    
    while((ptrav!=NULL) && (ptrav->infoIn!=Del))
    {
        pprev= ptrav;
        ptrav= ptrav->next;
    }                           //These functions should search for the

    // proper item to delete, and delete it
    if (pprev==ptrav) 
        return false;
    else
    if(pprev==NULL)
    { 
        plist= plist->next;
        delete ptrav;            
    }
    else
    {
        pprev->next =ptrav->next;
        delete ptrav;
    }

    return true;
}

Rejoice in the consistency of formatting no matter what editor or forum you post it on.

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Join Date: Dec 2007

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henpecked1 henpecked1 is offline

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Re: Linked List Delete

Aug 21st, 2008

My apologies for the formatting in my recent posts. I no longer have an IDE at work and must "troubleshoot" my errors in a text editor until I get home.

Unfortunately, it doesn't hold the formatting of an IDE well, and makes things even worse when it is copied and pasted into the forum.

I assure you my intent is not to confuse or irritate, nor bring your wrath down upon me. Your experience in this subject, and indeed on this board is vastly superior to mine and I only ask your patience since even after 200 posts, I am, by all standards, still a beginner in both.

Last edited by henpecked1; Aug 21st, 2008 at 5:39 pm.

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Re: Linked List Delete

Aug 21st, 2008

•

Help with Code Tags

C++ Syntax (Toggle Plain Text)
bool list::del(Contributor Del)
{
    Contributor infoIn=Del;     // Contributor is the object, 
                                // infoIn is the specific object
 
    node *pprev= plist;         // plist is the beginning of the list, 
                                // ptrav is what some
    node *ptrav= plist;         // would call "temp" or "head",
                                // and pprev is the "tail"
bool list::del(Contributor Del) { Contributor infoIn=Del; // Contributor is the object, // infoIn is the specific object node *pprev= plist; // plist is the beginning of the list, // ptrav is what some node *ptrav= plist; // would call "temp" or "head", // and pprev is the "tail"

Contributor is NOT an object. It looks like Contributor is a class or a struct. What relationship it has to the node class/struct is not clear. plist appears to have a type of node* and points to the first node in the list.

It appears that after this code is executed, pprev, plist, and ptrav are all pointing to the same node.

•

Help with Code Tags

C++ Syntax (Toggle Plain Text)
    if (pprev==ptrav)           //to delete from beginning of list
    {
 
        plist = ptrav->next;    //sends plist to next node
        delete ptrav;           //delete Node
    }
if (pprev==ptrav) //to delete from beginning of list { plist = ptrav->next; //sends plist to next node delete ptrav; //delete Node }

Since ptrav and pprev will always point to the same node at this point, this if statement is unnecessary since it will always evaluate to true. plist now points to the second node in the list. Is this if statement supposed to ALWAYS execute? If not, I'd put some debugging statement inside of it that displays something and find out if it is ever skipped. It appears to me that it is never skipped.

•

Help with Code Tags

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    while((ptrav!=NULL) && (ptrav->infoIn!=Del))
    {
        pprev= ptrav;
        ptrav= ptrav->next;
    }
while((ptrav!=NULL) && (ptrav->infoIn!=Del)) { pprev= ptrav; ptrav= ptrav->next; }

You define infoIn as type Contributor above. It also appears to be a data member of the node class/struct. So does each node store data of type Contributor and infoIn is the Contributor member of the node class? The function is passed not the node to delete itself but rather the data that the node to delete contains? If you aren't careful, using the same name for both a specific class/struct object and a class/struct data member can get confusing. The infoIn object form this line:

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(Toggle Plain Text)

Contributor infoIn=Del;

is never used as far as I can see, so can be deleted. It's different from the infoIn from this line:

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(Toggle Plain Text)

while((ptrav!=NULL) && (ptrav->infoIn!=Del))

I think you need to provide at least the header of the Contributor, list, and node classes/structs. Not the method implementation code itself, but the header that lists at least what each struct/class's data members are and how they relate to each other. Posting the entire header with the method declarations included could be helpful.

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Re: Linked List Delete

Aug 21st, 2008

Vernon,

Here is the code you requested. I would have posted it all, but it seemed like it would be terribly long, so I attached it instead.

Attached Files

	ContributorClass.h (2.4 KB, 9 views)
	NodeClass.h (246 Bytes, 10 views)
	ListClass.h (279 Bytes, 10 views)
	NodeClass.cpp (168 Bytes, 7 views)
	ListClass.cpp (2.0 KB, 12 views)
	contributor.cpp (3.5 KB, 6 views)
	List Main.cpp (637 Bytes, 10 views)

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Re: Linked List Delete

Aug 22nd, 2008

This won't compile. contributor.cpp has this line:

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#include "Contributor.h"

You haven't provided this file.

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henpecked1 henpecked1 is offline

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Re: Linked List Delete

#10

Aug 22nd, 2008

bah...I attached the wrong cpp file. try this one

and it should be asking for ContributorClass.h no space, add a space, whichever...I caught it after I attached it

Last edited by henpecked1; Aug 22nd, 2008 at 12:13 am.

Attached Files

Contributor class.cpp (4.9 KB, 11 views)