Singly-Linked Lists problem

[bsdpowa]

Me again, this time I really have a problem.
I'm trying to add an element before a certain element.
Example:
List: 1,2,3,4,5
Find: 2
Add: 45
List: 1,45,2,3,4,5

Now the thing is that when I find the number and try to add a new number it adds OK but then it deletes the last element of the list.
Example:
List: 1,2,3,4,5
Find: 2
Add: 45
List: 1,45,2,3,4

How do I fix this? This is my code below:

node* p_before = find_element(number, k_beginning);	//return a pointer to an element we're trying to find			
	node* p_after = p_before->k_next;						

	node* k_new= new node;
	k_new->number= number;
	k_new->k_next= k_after;
	p_before->k_next= k_new;

[Dave Sinkula]

I, for one, generally do much better at answering questions if the code posted is complete, yet small and fully compileable, and demonstrates the problem.

[bsdpowa]

But you don't need anything else because nothing is related to anything in the program.

add_before_element(5, p_beginning);

void add_before_element(int number, node*& p_beginning)
{
node* p_before = find_element(number, k_beginning);	//return a pointer to an element we're trying to find			
	node* p_after = p_before->p_next;						

	node* p_new= new node;
	p_new->number= number;
	p_new->p_next= p_after;
	p_before->p_next= p_new;
}

The code is not in english so I would need to translate everything but you don't really need it.

[Daishi]

node* p_before = find_element(number, k_beginning);

What is k_beginning? Is it a node? Is it a number? Is it suppose to be p_beginning?

In any case, that code shouldn't truncate the end of the list. But it still looks like bad code, what happens when you try to add before the first element?

-Fredric

[Rashakil Fol]

First of all, you passed p_beginning to the function and then tried to use k_beginning. Your code compiles?

Second, you expect us to have a crystal ball that can read your mind. What does "add_before_element" mean? Do you want to add before the element containing 'number'? Or do you want to add before the numberth element? Without explaining at all what find_element tries to do, this is still unknown.

And how in the world do you expect to insert the number 42 before the element either containing 2 or lying at the second position, using a function that gets passed only one integer?

[bsdpowa]

First of all, you passed p_beginning to the function and then tried to use k_beginning. Your code compiles?

Second, you expect us to have a crystal ball that can read your mind. What does "add_before_element" mean? Do you want to add before the element containing 'number'? Or do you want to add before the numberth element? Without explaining at all what find_element tries to do, this is still unknown.

And how in the world do you expect to insert the number 42 before the element either containing 2 or lying at the second position, using a function that gets passed only one integer?

Like I said, the code is not in english and I ruffly translated those pointers, don't mind the minor errors.
I really don't know what's so hard to understand? :)

I'd like to add an element BEFORE the specific element in the list.
add_before_element() is exactly what I'm trying to do, I explained that before.The first CODE quote was a simple call to the CODE quote below so you could picture things better passing a NUMBER I'd like to add and a pointer to the beginning.I'll explain once again for all of you who don't understand.

add_before_element(5, p_beginning);   //This is a line somewhere in the program which calls a function for adding an element before a certain element passing a number and pointer to the beginning

void add_before_element(int number, node*& p_beginning)   //This is a function that is being called
{
node* p_before = find_element(number, k_beginning);	//There is another function called find_element() for finding an element and instead of the element it returns a pointer to that element and that pointer is called p_before
	node* p_after = p_before->p_next;   //Now, since the p_before is a pointer to the already found element, we make p_after a poitner to the next element of the found one -> p_before->p_next				

	node* p_new= new node;   //We make a new node called p_new
	p_new->number= number;  //Now we insert a number (5) in the newly created node
	p_new->p_next= p_after;  //And now we link the newly created node
	p_before->p_next= p_new;  //Same goes here
}

The thing is that it adds a number fine but then it deletes the last number in the node.Here is the sample output:

Adding a number before a certain number
Our list contains: 5, 3, 4, 8, 1, 2
Before what element would you like to insert a number? 1
What element would you like to insert? 45
Our list after the operation: 3, 4, 8, 1, 45, 2

I also did the add_after_element() and it works fine.

[bsdpowa]

node* p_before = find_element(number, k_beginning);

What is k_beginning? Is it a node? Is it a number? Is it suppose to be p_beginning?

In any case, that code shouldn't truncate the end of the list. But it still looks like bad code, what happens when you try to add before the first element?

-Fredric

Hmm, it looks like it adds after the element.Here is the sample output:

Our list: 3, 2, 1 (I first input 1 then 2 then 3)
Element you'd like to add before? 1
Number: 45
Our list: 2, 45, 1

[Daishi]

How are you printing out the list?

-Fredric

[bsdpowa]

I'm printing it out this way:

void print_out(node*& p_beginning)
{
	node* p_print = p_beginning;							

	while (p_print != 0)
	{
		cout << p_print->number << " ";						
                p_print = p_print->p_next;
	}
	cout << endl;
}