C / C++ / MFC

image processing toolkits | batch image processing

7-Jun-15 4:28

well im trying to delete some nodes from my list and search for them using 2 different functions

problem is that deleteNode it just doesnt work (not even an error msgs)
when i activate the print list function it stays the same

could someoen help me with this?

deletes the node:
numStruct* deleteNode(numStruct** firstNode, numStruct* nodeToDelete)
{
numStruct* currNode = *firstNode;
numStruct* temp;

// if the list is not empty
if (*firstNode)
{
// the first node should be deleted
if (currNode == nodeToDelete)
{
*firstNode = (*firstNode)->Next;
free(currNode);
}
else
{
while (nodeToDelete != currNode->Next && currNode->Next)
{
currNode = currNode->Next;
}

if (nodeToDelete == currNode->Next && nodeToDelete)
{
temp = currNode->Next;
currNode->Next = temp->Next;
free(temp);
}
}
}

printf("\n\n");
}

this is my main:

case 2:
{
numStruct* t = anchorNode;
int arr[50] = { 261363 }, spot = 0;

printf("Please enter all the numbers you want to delete and end it with - 999 \n");

while ((arr[spot] != -999) && (spot != 50))
{
scanf("%d", &arr[spot]);

if (arr[spot] != -999)
{
spot++;
}
}

if (arr[spot] == -999)
{
arr[spot] = 261363;
spot--;
}

for (int i = 0; i < spot; i++)
{
int flag = 0;
while ((t->number != arr[i]) && (t->number != NULL))
{

t = t->Next;
if (t->number == arr[i])
{
flag = 1;
}
}

if (flag == 1)
{
deleteNode(anchorNode, t);
t = anchorNode;
}

}

break;
}

Re: linked list in C

C^hris L^osinger9-Jun-15 4:55

C^hris L^osinger

9-Jun-15 4:55

i'd start looking here:

numStruct* deleteNode(numStruct** firstNode, numStruct* nodeToDelete)

fn takes a pointer to a pointer to a numStruct.

but here:

numStruct* t = anchorNode;
...
deleteNode(anchorNode, t);

you're just passing a pointer to a numStruct.

need help with linked structs at C language

a random user5-Jun-15 23:57

5-Jun-15 23:57

i recently studied about this subject and i tried to code a program that does some stuff connected to it
but i ran into troubles while tryign to add more structs with numbers
i cutted mose of my program (to your convinient)

please help me to udnerstand my mistakes

http://pastebin.com/nyj3wtXT[^]

Richard MacCutchan6-Jun-15 0:29

Richard MacCutchan

6-Jun-15 0:29

Please add some proper detail to your question and include your code here rather than offsite.

a random user6-Jun-15 0:56

6-Jun-15 0:56

well i first created the code to work on the main but somehow somethign went wrong when i tried putting the codes in functions
<
every time i go to the function insertAtEnd but at the second loop of the while it just says error

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

struct numberNode
{
int number;
struct numberNode* Next;
};

typedef struct numberNode numStruct;

numStruct* createSong(int numbers)
{
numStruct* newSong = (numStruct*)malloc(sizeof(numStruct));
if (newSong)
{
newSong->number = numbers;
newSong->Next = NULL;
}
return newSong;
}

void insertAtEnd(numStruct** firstNode, numStruct* newNode)
{
numStruct* currNode = *firstNode;

// if the linked list is empty
// should put the new node as the first
if (!currNode)
{
*firstNode = newNode;
newNode->Next = NULL;
}
else
{
while (currNode->Next) // problem at the second loop
{
currNode = currNode->Next;
}

currNode->Next = newNode;
newNode->Next = NULL;
}
printf("\n\n");
}

numStruct* AddSongs(numStruct* anchorNode, numStruct* newNode)
{

int count = 0;
int numbers;

printf("\nPlease enter numbers and at the end enter -999\n");

do
{
count++;
_flushall();
numbers = 0;

printf("\n\n%d.\n\nnumber: ", count);
scanf("%d",&numbers);

if (numbers != -999)
{

newNode = createSong(numbers);
insertAtEnd(&anchorNode, newNode);
}
}
while (numbers != -999);
printf("\n\n");
}

int main(void)
{
numStruct* anchorNode = NULL;
numStruct* newNode;
AddSongs(&anchorNode, &newNode);

system("PAUSE");
}

Frankie-C6-Jun-15 6:42

6-Jun-15 6:42

Your code is almost correct, just a couple of errors in the main function.
The variable newNode have to be initialized to NULL to avoid errors and compiler complainings.
anchorNode and NewNode are already pointer to structures of type numStruct, so you have to pass them directly to AddSongs(), but you're passing their address (even if this sounds strange to me because you should have got a compiler error).
The correct code is this:

C++

int main(void)
{
    numStruct* anchorNode = NULL;
    numStruct* newNode = NULL;    
    AddSongs(anchorNode, newNode);
 
    system("PAUSE");
}

a random user6-Jun-15 7:03

6-Jun-15 7:03

ok then if thats the case why
does this next function doesnt work after making the linked list

void printList(numStruct* firstNode)
{
numStruct* currSong = firstNode;
printf("\n\n-------------------------------------\n");
while (currSong)
{
printf("number= %d \n", currSong->number);
currSong = currSong->Next;
}
printf("-------------------------------------\n\n");
printf("\n\n");
}

which in main it will look like this

int main(void)
{
numStruct* anchorNode = NULL;
numStruct* newNode = NULL;
AddSongs(anchorNode, newNode);
printList(anchorNode);

system("PAUSE");
}

Frankie-C6-Jun-15 7:12

6-Jun-15 7:12

Because just the first variable anchorNode must be passed as pointer to struct pointer to have it assigned. Also AddSongs must pass it directly to insertAtEnd().
I report the whole program here:

C++

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

struct numberNode {
	int number;
	struct numberNode *Next;
};

typedef struct numberNode numStruct;

numStruct *createSong(int numbers)
{
	numStruct *newSong = (numStruct *)malloc(sizeof(numStruct));
	if (newSong)
	{
		newSong->number = numbers;
		newSong->Next = NULL;
	}
	return newSong;
}

void insertAtEnd(numStruct **firstNode, numStruct *newNode)
{
	numStruct *currNode = *firstNode;

	// if the linked list is empty
	// should put the new node as the first
	if (!currNode)
	{
		*firstNode = newNode;
		newNode->Next = NULL;
	}
	else
	{
		while (currNode->Next)	// problem at the second loop
		{
			currNode = currNode->Next;
		}

		currNode->Next = newNode;
		newNode->Next = NULL;
	}
	printf("\n\n");
}

numStruct *AddSongs(numStruct **anchorNode, numStruct *newNode)
{
	int count = 0;
	int numbers;

	printf("\nPlease enter numbers and at the end enter -999\n");

	do
	{
		count++;
		//flushall();
		fflush(stdin);
		numbers = 0;

		printf("\n\n%d.\n\nnumber: ", count);
		scanf("%d", &numbers);

		if (numbers != -999)
		{
			newNode = createSong(numbers);
			insertAtEnd(anchorNode, newNode);
		}
	}
	while (numbers != -999);
	printf("\n\n");
	return NULL;
}

void printList(numStruct *firstNode)
{
	numStruct *currSong = firstNode;
	printf("\n\n-------------------------------------\n");
	while (currSong)
	{
		printf("number= %d \n", currSong->number);
		currSong = currSong->Next;
	}
	printf("-------------------------------------\n\n");
	printf("\n\n");
}

int main(void)
{
	numStruct *anchorNode = NULL;
	numStruct *newNode = NULL;
	AddSongs(&anchorNode, newNode);
	printList(anchorNode);

	system("PAUSE");
}

Check it against your code.
We pass a pointer to a variable when we want access the variable from the called function, in your case to assign to anchorNode the beginning of the memory list.

a random user6-Jun-15 7:20

6-Jun-15 7:20

that worked perfectly thank you very much

a random user6-Jun-15 7:25

6-Jun-15 7:25

there is one more thing that bothers me

1 more problem im having in my full program is to "delete" a part of the linked list
and reconnect it to the others by an input

i tried to do this next thing:

void deleteNode(numStruct** firstNode, numStruct* nodeToDelete)
{
numStruct* currNode = *firstNode;
numStruct* temp;

// if the list is not empty
if (*firstNode)
{
// the first node should be deleted
if (currNode == nodeToDelete)
{
*firstNode = (*firstNode)->Next;
free(currNode);
}
else
{
while (nodeToDelete != currNode->Next && currNode->Next)
{
currNode = currNode->Next;
}

if (nodeToDelete == currNode->Next && nodeToDelete)
{
temp = currNode->Next;
currNode->Next = temp->Next;
free(temp);
}
}
}

inside the main:
numStruct* t = anchorNode;
int arr[50] = { 261363 }, spot = 0;

printf("Please enter all the numbers you want to delete and end it with - 999 \n");

while ((arr[spot] != -999) && (spot != 50))
{
scanf("%d", &arr[spot]);

if (arr[spot] != -999)
{
spot++;
}
}

if (arr[spot] == -999)
{
arr[spot] = 261363;
spot--;
}

for (int i = 0; i < spot; i++)
{
int flag = 0;
while ((t->number != arr[i]) && (t->number != NULL))
{

t = t->Next;
if (t->number == arr[i])
{
flag = 1;
}
}

if (flag == 1)
{
deleteNode(anchorNode, t);
t = anchorNode;
}

}

the problem is that it doesnt really delete it
when i go beck to the menu and do the print function again it appears the same

Frankie-C7-Jun-15 5:33

7-Jun-15 5:33

There are a lot of errors and redundant code.
See the following solution, study it and go on on yourself now.

C++

void deleteNode(numStruct **firstNode, numStruct *nodeToDelete)
{
	numStruct *temp = NULL;

	if (!*firstNode)
		return;	//Empty list

	// Special case the node we must delete is the first one
	if (*firstNode == nodeToDelete)
	{
		temp = *firstNode;
		*firstNode = (*firstNode)->Next;
		free(temp);
		return;
	}

	for (numStruct * currNode = *firstNode; currNode->Next; currNode = currNode->Next)
	{
		if (nodeToDelete == currNode->Next)
		{
			temp = currNode->Next;
			currNode->Next = (currNode->Next)->Next;
			free(temp);
			return;
		}
	}
}

void RemoveNodes(numStruct **anchorNode)
{
	numStruct *t = *anchorNode;
	int arr[50] = {0};
	int spot = 0;

	printf("Please enter all the numbers you want to delete and end it with - 999 \n");

	for (spot=0; spot < 50; spot++)
	{
		fflush (stdin);
		scanf("%d", &arr[spot]);
		if (arr[spot] == -999)
			break;
	}

	if (spot >= 50)
		spot--;

	for (int i = 0; i < spot; i++, t = *anchorNode)
	{
		while (t != NULL)
		{
			if (t->number == arr[i])
			{
				deleteNode(anchorNode, t);
				break;
			}
			t = t->Next;
		}
	}
}

int main(void)
{
	numStruct *anchorNode = NULL;
	numStruct *newNode = NULL;
	AddSongs(&anchorNode, newNode);
	printList(anchorNode);

	RemoveNodes(&anchorNode);
	printList(anchorNode);

	system("PAUSE");
}

a random user7-Jun-15 6:32

7-Jun-15 6:32

thats brilliant thank you very very much!!

Frankie-C7-Jun-15 7:38

7-Jun-15 7:38

Thanks.

David Crow8-Jun-15 3:20

David Crow

8-Jun-15 3:20

a random user wrote:
the problem is that it doesnt really delete it

So have you stepped through each line of code using the debugger? Short of doing that, asking questions and pasting others' code snippets into your project are just a waste of time.

a random user21-Jun-15 9:37