Help in Linked List Operations

[aren34]

Guys, please help me with these operations on linked list will ya? Please..

a. initializeList – to initialize the count to 0 and head to null.

b. deleteList – to delete any nodes in the linked list.

c. listEmpty – check if the linked list is empty.

d. printList – to print each number in the linked list.

this is my header file.

#ifndef LINKEDLISTH

#define LINKEDLISTH

typedef int ListEntry;

typedef struct listnode {

ListEntry entry;
struct listnode *nextnode;

} ListNode;

typedef int Position;

typedef struct list {
int count;
ListNode *head;
} List;

ListNode *makeListNode(ListEntry x);
void setPosition(Position p, List *L, ListNode **current);
void insertList(Position p, ListEntry x, List *L);
void Error(const char *ErrorDesc);
void initializeList(List *ptr);
void deleteList();
void printList(ListNode *L);



#endif

this is my main file.

//This file contains all functions implementation in linkedlist.h

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "linkedlist.h"

int main(void)
{
	List *pList;
	ListNode *listnode;
	ListEntry x;
	Position p;

	initializeList(&pList); //question 1 a

	printf("Enter the number of nodes: ");
	scanf("%d", &p);
	printf("Enter values:");
	scanf("%d", &x);
	while (x!=-999)
		{
		insertList(p, x, &pList);
		scanf("%d", &x);
		}
		
	printList(&listnode);
	deleteList();
	
	return 0;
}


//read data n put the data into a structure
ListNode *makeListNode(ListEntry x)
{
	ListNode *newPtr = (ListNode*)malloc(sizeof(ListNode));

   if (newPtr == NULL) {
      Error("Out of memory");
   }
   else {

		newPtr->entry = x;
		newPtr->nextnode = NULL;
   }

   return newPtr;
}


void setPosition(Position p, List *L, ListNode **current)
{
	int i;

	ListNode *nodePtr = L->head;
	*current = nodePtr;

	if( p < 0 || p > L->count )
	{
		Error("Invalid position\n");
	}
	else
	{
		for ( i = 0; i < p; i++)
		{
			nodePtr = nodePtr->nextnode;
			*current = nodePtr;
		}
	}
}

void insertList(Position p, ListEntry x, List *L)
{
	ListNode *newNodePtr = makeListNode( x );
	ListNode *prevPtr = NULL;

	if ( p == 0 )
	{
		newNodePtr->nextnode = L->head;
		L->head = newNodePtr;
	}
	else
	{
		setPosition( p-1,L,&prevPtr );
		prevPtr->nextnode = newNodePtr;
	}
	L->count++;
}

void Error(const char *ErrorDesc)
{
	printf("%s",ErrorDesc);
}

void initializeList(List *ptr)
{
	ptr->count=0;
	ptr->head=NULL;
}

void deleteList(List *pList)
{
	int numDelete;
	ListNode *pPre;
	ListNode *pCur;

	pCur=pList->head;

	printf("Enter integer to be deleted : ");
	scanf("%d", &numDelete);
		while (pCur!=NULL)
		{
			if (pCur->entry==numDelete)
			{
				pPre->nextnode=pCur->nextnode;
				free(pCur);
			}
			else
				pCur=pCur->nextnode;
		}
}


void printList(ListNode *L) {
		while(L!=NULL) {
			printf("%d\t", L->entry);
			L = L->nextnode;
		}
	}

Please correct me if there is any mistake..

[Salem]

Use [code][/code] tags for posting code please.
You should still be able to edit your post to correct this.

[aren34]

ok.. first timer here.. sorrry..

[Subsonics]

What is your thought behind this?

printf("Enter values:");
scanf("%d", &x);
while (x!=-999)
{
	insertList(p, x, &pList);
	scanf("%d", &x);
}

You start to asking for number of nodes. Is -999 suppose to be an exit condition that you enter manually?

[aren34]

What is your thought behind this?

printf("Enter values:");
scanf("%d", &x);
while (x!=-999)
{
	insertList(p, x, &pList);
	scanf("%d", &x);
}

You start to asking for number of nodes. Is -999 suppose to be an exit condition that you enter manually?

I wish to prompt user to enter a series of number and if user want to exit, he/she has to enter -999.. And print out the lists.. Please help me out. thanks!

[Subsonics]

One thing I note is that:

List *pList;

// is used like this

initializeList(&pList);

When the implementation looks like this:

void initializeList(List *ptr)
{
    ptr->count=0;
    ptr->head=NULL;
}

List *pList, is only a pointer variable not an actual List type. You would need to declare it like this: List list;

[aren34]

One thing I note is that:

List *pList;

// is used like this

initializeList(&pList);

When the implementation looks like this:

void initializeList(List *ptr)
{
    ptr->count=0;
    ptr->head=NULL;
}

List *pList, is only a pointer variable not an actual List type. You would need to declare it like this: List list;

Declare as List list? Would you enlighten me pls? I'm really bad in this linked list stuffs..

[Subsonics]

I wish to prompt user to enter a series of number and if user want to exit, he/she has to enter -999.. And print out the lists.. Please help me out. thanks!

So it's an exit condition. I just thought it was odd since you did just ask for the number of nodes just before, but then continue on ignoring this and instead use "number of nodes" as a position. In an empty list there is only one valid position.

Declare as List list? Would you enlighten me pls? I'm really bad in this linked list stuffs..

Basically get rid of the *.


Edit: I would recommend that you (temporarily) get rid of what you now have in main(), then test each list function separately to make sure they all work as intended in isolation.

[aren34]

So it's an exit condition. I just thought it was odd since you did just ask for the number of nodes just before, but then continue on ignoring this and instead use "number of nodes" as a position. In an empty list there is only one valid position.




Basically get rid of the *.


Edit: I would recommend that you (temporarily) get rid of what you now have in main(), then test each list function separately to make sure they all work as intended in isolation.

After i get rid of the *, i get these error..
1>c:\users\acer\desktop\data structure assignment 2\linkedlist.c(15) : error C2440: 'function' : cannot convert from 'List *' to 'List'
1>c:\users\acer\desktop\data structure assignment 2\linkedlist.c(15) : warning C4024: 'initializeList' : different types for formal and actual parameter 1
1>c:\users\acer\desktop\data structure assignment 2\linkedlist.c(23) : warning C4047: 'function' : 'List *' differs in levels of indirection from 'List **'
1>c:\users\acer\desktop\data structure assignment 2\linkedlist.c(23) : warning C4024: 'insertList' : different types for formal and actual parameter 3
1>c:\users\acer\desktop\data structure assignment 2\linkedlist.c(27) : warning C4047: 'function' : 'ListNode *' differs in levels of indirection from 'List **'
1>c:\users\acer\desktop\data structure assignment 2\linkedlist.c(27) : warning C4024: 'printList' : different types for formal and actual parameter 1
1>c:\users\acer\desktop\data structure assignment 2\linkedlist.c(98) : error C2232: '->count' : left operand has 'struct' type, use '.'
1>c:\users\acer\desktop\data structure assignment 2\linkedlist.c(99) : error C2232: '->head' : left operand has 'struct' type, use '.'


Regarding the nodes things, Does this mean i have to ignore the number of nodes? and let p=0? if i dun initialize p, error will pop out..

So it's an exit condition. I just thought it was odd since you did just ask for the number of nodes just before, but then continue on ignoring this and instead use "number of nodes" as a position. In an empty list there is only one valid position.



Basically get rid of the *.


Edit: I would recommend that you (temporarily) get rid of what you now have in main(), then test each list function separately to make sure they all work as intended in isolation.

Sorry that I juz saw your Edit... how do i test each function without using the main? Im really troubling you a lot, sir..

[Subsonics]

Look at your own insertList implementation. the variable 'p' is used to mark a position in the list. Regarding the errors, again look at your own initializeList function, you need to send the address of an actual existing node since you are manipulating that node in the function. An empty pointer wont do. If you get errors further down, then test each function separately to isolate the problem instead of trying to solve everything at once.

[aren34]

Look at your own insertList implementation. the variable 'p' is used to mark a position in the list. Regarding the errors, again look at your own initializeList function, you need to send the address of an actual existing node since you are manipulating that node in the function. An empty pointer wont do. If you get errors further down, then test each function separately to isolate the problem instead of trying to solve everything at once.

hmmm.. the p is to mark the position in the list, but how do i manipulate it?

i'll try to fix the initializeList function.. and is there a way to test the functions one by one without dealing with the main function?

[Subsonics]

hmmm.. the p is to mark the position in the list, but how do i manipulate it?

I don't know, the way you use it in main(), on an empty list p should probably be zero.

i'll try to fix the initializeList function.. and is there a way to test the functions one by one without dealing with the main function?

There is nothing wrong with your initializeList function. You could just wrap your current main() inside /* */ then create a new temporary one to test the functions one by one. For example create a single node and add 1 value. Does it work? etc.

[aren34]

could you give me an example on creating a single node, add value and print?

[Subsonics]

You could do this:

int main()
{
    List list;

    initializeList(&list);
    insertList(0, 123, &list);

    return 0;
}

Print wont work since you have created a special struct for the node, in your current code '*listnode' is an empty pointer, I don't see how you could use it to print the list, it's unrelated to the list.

[aren34]

You could do this:

int main()
{
    List list;

    initializeList(&list);
    insertList(0, 123, &list);

    return 0;
}

Print wont work since you have created a special struct for the node, in your current code '*listnode' is an empty pointer, I don't see how you could use it to print the list, it's unrelated to the list.

I see.. I tried the one you wrote here.. It got no error however there is nothing shown on the command prompt.. just a line "press any key to continue..."

hmm.. Actually what I'm blur here is that I got List and ListNode.. dont know how to differentiate between them I never know ListNode is empty in this situation...