Linked List Help

[kerrywolfe]

Hey all the Gurus out there...need a little assistance with adding a node and deleting a node...I have the code below...hopefully somebody can make something out of the mess!!!

THIS TESTS THE ADDING:

void TestAddNode (NodePtr List)
{
char NewChar;

cout << "\n\n---------------- Testing AddNode -------------------\n\n";

cout << "Character to be added? ";
NewChar = getch();

if (NewChar == '\r') // User pressed just enter key.
{
cout << "Aborting AddNode...";
return;
}

cout << NewChar;
cout << " -- Adding \'" << NewChar << "\'";

AddNode (NewChar, List);

cout << "\n\nThe new list: ";
ShowList(List);
}

THIS IS TRYING TO ADD THE NODE:

void AddNode (char NewChar,
NodePtr List)
{
NodePtr NewNode;

NewNode = List;

if (NewChar != '\n')
{
NewNode->Link = new Node;

if (NewNode->Link == NULL)
AbortProgram();

else
{
NewNode = NewNode->Link;
NewNode->Ch = NewChar;
NewNode->Link = NULL;
}
}
}

THIS IS TO TEST DELETE NODE:

void TestDeleteNode (NodePtr List)

{
int CharFound;
char CharToBeDeleted;


cout << "\n\n***************** Testing DeleteNode *******************";

cout << "\n\nCharacter to be deleted? ";
CharToBeDeleted = getch();
cout << CharToBeDeleted;

DeleteNode (CharToBeDeleted, List, CharFound);

if ( CharFound )
cout << "\n\n'" << CharToBeDeleted << "' has been deleted,";
else
cout << "\n\n'" << CharToBeDeleted << "' was not in the list,";

cout << "\n\nList = ";
ShowList(List);
}


THIS IS FOR DELETING NODE:

void DeleteNode (char CharToDelete,
NodePtr List,
int &CharFound)
{
NodePtr NodeToBeDeleted;

if (List->Ch == CharToDelete)
{
NodeToBeDeleted = List;
List = List->Link;
delete NodeToBeDeleted;
List->Link = NULL;
CharFound = 1;
}
else
CharFound = 0;
}


ANY HELP WOULD BE MUCH APPRECIATED!!!

Thanks!

[zen]

You haven't really shown enough of your code or stated what error messages you're getting, but here's a few points that may or may not be applicable -

1) Does List always point to the last node added to your list? If not you'll either have to store the end of your list in a pointer and pass this into AddNode(), or traverse the list everytime you call AddNode(). Otherwise you'll be adding a character in the same position and losing pointers to all the other characters added.

2) Add node will only work if the list already exists.

3) When deleteing a character you'll probably want to traverse the list to find it, at present you're only checking one node.

4) If you are deleting the last node then List = List->Link; will make List=NULL, and then doing List->Link = NULL; will probably crash your program, as you cannot access members of objects that don't exist. You'll want to check to see if you're deleting the head or tail of the list and take the appropriate action.

[kerrywolfe]

Okay,

i understand what you are saying....I got the Add NOde to work now....the LIST DOES EXIST already. Its a lot of code and I was trying to save the time of going through alot of what doesn't matter....

For the Delete Node....the user is asked to enter a char to delete from the list that they have built already. That is the NewChartoDelete variable.

I dont understand how to go node to node to find the match and then delete that node....this only has to work for the first occurence of the character even if there are multiple ones present

As Always, Any Help is Appreciated!

[zen]

dont understand how to go node to node to find the match and then delete that node

You can loop through the list -


NodePtr It = List;

while(It != NULL)
{
if(It->Ch== CharToDelete)
{
//Delete node
//Re-link list
//Set flag to indicate that char has been deleted
//Break from loop
}
It=It->Link;
}


The only bit that needs some work is the re-linking.