Whats wrong with this linked list?

[Mythios]

Any time values get entered into the list nothing happens nor have they been added. Here's a sample of what I've done but I'm getting a little confused whats wrong with it.

main.cpp

int main()
{

	// The beginning node in the linked list.
	Node *pFirstNode = NULL;

	//Used to move along the linked list
	Node *pCurrentNode = pFirstNode;

	int option = 0;
	
	do
	{
		DisplayLinkedList( pFirstNode, pCurrentNode );

		printf( "\nPlease select an option : " );
		printf(	"\n0. Exit the program." );
		printf(	"\n1. Add a node to the end of the list.");
		printf(	"\n2. Delete the start node from the list.");
		printf(	"\n3. Delete the end node from the list.");
		printf(	"\n4. Move the current pointer on one node.");
		printf(	"\n5. Move the current pointer back one node.\n\n  >> ");
		scanf_s( "%d", &option );

		switch (option)
		{
			case 1 : 
				AddNode( pFirstNode, pCurrentNode );
				break;

			case 2 : 
				DeleteStartNode( pFirstNode );
				break;

			case 3 : 
				DeleteEndNode( pFirstNode );
				break;

			case 4 : 
				MoveCurrentNodeForward( pCurrentNode );
				break;

			case 5 : 
				MoveCurrentNodeBack( pFirstNode, pCurrentNode );
				
		}
	}while( option != 0 );

	return 0;
}

Linked List Functions

void AddNode( Node *pStart, Node *pCurrent )
{
	// Temporary pointers
	Node *pTemp, *pTempTwo;

	// Reserve space for new node and fill it with data
	pTemp = new Node;
	
	// User data entry for a new node
	printf( "Please enter the age of the person : " );
	scanf_s( "%d", &pTemp->age );
	printf( "Please enter the height of the person : " );
	scanf_s( "%f", &pTemp->height);

	pTemp->next = NULL;

	// Set up link to this node
	if( pStart == NULL )
	{ 
		pStart = pTemp;
		pCurrent = pStart;
	}
	else
	{ 
		pTempTwo = pStart;

		// We know this is not NULL - list not empty!
		while ( pTempTwo->next != NULL )
		{  
			pTempTwo = pTempTwo->next;
			// Move to next link in chain
		}
		pTempTwo->next = pTemp;
	}
}

[jsmith]

I believe you were intending that AddNode() modify pStart and/or pCurrent and actually have main's version of pFirstNode and pCurrentNode be changed by AddNode(), but that is not the case.

Make AddNode take its two pointer parameters by reference.

[Mythios]

I know how to take it by reference but is it possible to do it at all by taking it by pointers?

[jsmith]

Pointer to pointer is the alternative.

[Mythios]

Could you explain exactly what you mean to that? As thats what I thought I was basically doing.

Thanks jsmith.

[jsmith]

AddNode would need to be declared like this:

void AddNode( Node **pStart, Node **pCurrent )

[Mythios]

Yup thats fine, but the inside of the function itself I'm a little confused on how I should be doing it. Because pCurrent = pStart; and **pCurrent = **pStart; both compile for example but I'm not to sure if I should be using one or the other. As the way I have it compiles but it crashes when I user input the age. Debug just tells me age = -87####### so I'm a tad confused :(

Thanks

[Mythios]

All good fixed now :)

Thanks.