Thread: delete a node from an array of linked lists

hi there

i have an array of linked lists, 10 of them to be precise. insertion works beautifully but deletion is a problem.

i want a function which returns an int upon deletion. 0 if the node is not in the array or 1 if it is and it was deleted. but, of course, it doesn't work.

here is my code:

Code:

int Delete(node *table[], int key)
{
	node *temp, *del;
	int i;
	int test = 0;
		
	for (i=0; i<10; i++)
	{
		temp = table[i];
		if (temp != NULL)
		{
			while (temp->key != key && temp != NULL)
			{
				del = temp;
				temp = temp->next;
			}
			
			if (temp == NULL) continue;	
			else if (temp->key == key) 
			{
					del->next = temp->next;
					free(temp);
					test = 1;
			}
		}
		else continue;		
	}
	return(test);
}

>>while (temp->key != key && temp != NULL)
This can cause a seg fault. You need to make it
while(temp && temp->key != key)
as to make it short on temp == NULL first.
Also, if temp == the one you want to delete, you need to save temp, then make the node BEFORE it point to temp->next. This will remove that node from the list, then you can free it. As soon as you free it you should return (unless you are attempting to delete multiple keys from the table -- which would be kinda odd).

Nope, still doesn't work! It doesn't delete the node i want when it does exist, but it does return 0 when i try to delete a non-existing node.

I colored the new lines of code red

Code:

int Delete(node *table[], int key)
{
	node *temp, *del, *save;
	int i;
	int test = 0;
		
	for (i=0; i<10; i++)
	{
		temp = table[i];
		if (temp != NULL)
		{
			while (temp && temp->key != key)
			{
				del = temp;
				temp = temp->next;
			}
			
			if (temp == NULL) continue;	
			else if (temp->key == key) 
			{
					save =  temp;
					del->next = temp->next;
					free(save);
					test = 1;
			}
		}
		else continue;		
	}
	return(test);
}

I wasn't expecting for all my problems to be solved. The fact that on this forum one doesn't get the code wrapped up in shiny paper is a great plus for me as it is more important to realise why something doesn't work as apart from how it should be written.

Thanks for your suggestions iMalc and to you Kennedy too, I re-did my code and now it works as expected:

Code:

int Delete(node *table[], int key)
{
	node *temp, *del;
	int i;
	int test = 0;
		
	for (i=0; i<10; i++)
	{
		temp = table[i];
		if (temp != NULL)
		{
			if (temp->key == key)
			{
				table[i] = temp->next;
				free(temp);
				test++;
			}
			else
			{
				while (temp && temp->key != key)
				{
					del = temp;
					temp = temp->next;
				}

				if (temp)
				{
					del->next = temp->next;
					free(temp);
					test ++;
				}
			}
		}		
	}
	return(test);
}

I guess I could/should have included a break in the for loop after it finds the sought node