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Plz Help! Deleting a node from a Linked List

crankage3 (3)
Write your question here.

Hello! i keep getting an error when the compiler gets to the while loop. I want to use this function to delete a node that contains a certain element.
the struct is
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struct NODE
{
	int num;
	NODE *next;
};


It says, "First-chance exception at 0x013A9540 in LLP.exe: 0xC0000005: Access violation reading location 0x00000000."

i have no idea what that means and I been stuck all day

don't mind the spacey formating
please help!!!


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  void removieitem(NODE *&Top, int remitem)
{
	NODE *ptr =NULL ,*ptr2 = NULL;
	ptr = Top;
	if(ptr==NULL)
		cout<<"There is no list"<<endl;
	else
	{
		if(ptr->num==remitem)
		{
			Top = Top->next;
			ptr->next=NULL;
			delete ptr;
		}
		else
		{
			ptr2 = ptr;
			ptr = ptr->next;

			while(ptr!=NULL || ptr->num!=remitem)
			{
				ptr2 = ptr;
				ptr = ptr->next;
			}
				if(ptr==NULL)
					cout<<"The element is not in the list"<<endl;
				else 
					if(ptr->next==NULL)
					{
						ptr2->next = NULL;
						delete ptr;
					}
					else
					{
						ptr2->next=ptr2->next->next;
						ptr->next=NULL;
						delete ptr;
					}

		}
	}
	
}
keskiverto (10367)
ptr!=NULL || ptr->num!=remitem
Well, if ptr IS null, then you have to check the ptr->num, which by definition does not exist.
Try ptr!=NULL && ptr->num!=remitem
yulingo (233)
Well, for starters, your first function parameter doesn't make any sense.
void removieitem(NODE *&Top, int remitem)
should probably be
void removieitem(NODE *Top, int remitem)
because you're trying to pass in a pointer to the beginning of the list. What you're currently passing in is the address of the pointer to the beginning of your list.
Last edited on
crankage3 (3)
Thank you keskiverto! it works perfectly
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void removieitem(NODE *&Top, int remitem)
{
	NODE *ptr =NULL ,*ptr2 = NULL;
	ptr = Top;
	if(ptr==NULL)
		cout<<"There is no list"<<endl;
	else
	{
		if(ptr->num==remitem)
		{
			Top = Top->next;
			ptr->next=NULL;
			delete ptr;
		}
		else
		{
			ptr2 = ptr;
			ptr = ptr->next;

			while(ptr!=NULL && ptr->num!=remitem)
			{
				ptr2 = ptr;
				ptr = ptr->next;
			}
				if(ptr==NULL)
					cout<<"The element is not in the list"<<endl;
				else 
					if(ptr->next==NULL)
					{
						ptr2->next = NULL;
						delete ptr;
					}
					else
					{
						ptr2->next=ptr2->next->next;
						ptr->next=NULL;
						delete ptr;
					}

		}
	}
	
}


The reason I used the '&' is because there is a chance that the node that I am removing would be in the front of the list. So if the "Top" of the list changed i would be able to pass that by reference. It's worked for my other code.

 
 
void removieitem(NODE *&Top, int remitem)
Last edited on
yulingo (233)
Are you writing this in C? Why aren't you just using a class?
crankage3 (3)
C++...have not tried that yet with linked lists because Structs are what they asked for...ill start practicing those soon
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