Deleting nodes from a linked list

This is a discussion on Deleting nodes from a linked list within the C Programming forums, part of the General Programming Boards category; Hello! I'm struggling a bit with the function of deleting a node from a linked list. I've made an attempt, ...

  1. #1
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    Deleting nodes from a linked list

    Hello! I'm struggling a bit with the function of deleting a node from a linked list. I've made an attempt, and it works fine if the node being deleted is the first node. However, if I want to delete any other node, the function hangs and just starts printing off whatever I input into they keyboard. I've included my node definition and the two functions I was trying to implement.

    Thanks in advance!

    Code:
    typedef struct node
    {
           char last[1024];
           char first[1024];
           char position;
           int value;
           struct node *link;
    }Node;
    Code:
    Node* deleteNode(Node *head)
    {
    char lastName[MAX_LENGTH+1];
    safegets(lastName,MAX_LENGTH+1);
    bool found = false;
    if (head == NULL)
    	return NULL;
    
    if (strcmp((head->last),lastName)==0)
    	{
    	Node *temp = head->link;
    	free(head);
    	return temp;
    	}
    Node *current = head;
    
    while (!found && (current->link)!=NULL)
    	{
    	if (strcmp((current->link->last),lastName)==0)
    		found==true;
    	else 
    		current=current->link;
    	}
    
    if (current->link!=NULL)
    	{
    	Node *temp = current->link;
    	(current->link)=(current->link->link);
    	free(temp);
    	return head;
    	}
    
    
    else if (current->link==NULL)
    	{
    	if(strcmp((current->last),lastName)==0)
    		deleteLast(head);
    	}
    	return head;
    }
    
    void deleteLast(Node *head)
    {
    Node *current = head;
    while (current->link->link != NULL)
    	current=current->link;
    free(current->link);
    current->link=NULL;
    }

  2. #2
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    For starters, lastName is a local variable and you don't ever prompt the user to enter one, so it is left uninitialized. Your comparisons will fail since there's garbage data in lastName, thus it will never find the person to delete. Make lastName a parameter to be passed into delete, so you call deleteNode(list_of_people, lastname_of_person_to_delete).

    Your delete code looks more or less fine, if a bit unconventional. But it's hard to say without enough code to compile and test your function. A main with some test data or input routines and an insertNode would be great.

  3. #3
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    when you found the node to be delete, you should break out the while,
    Code:
    while (!found && (current->link)!=NULL)
    	{
    	if (strcmp((current->link->last),lastName)==0)
                    {
    		found==true;
                                    break;
                    }
    	else 
    		current=current->link;
    	}

  4. #4
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    Quote Originally Posted by Jesius View Post
    when you found the node to be delete, you should break out the while,
    Code:
    while (!found && (current->link)!=NULL)
    	{
    	if (strcmp((current->link->last),lastName)==0)
                    {
    		found==true;
                                    break;
                    }
    	else 
    		current=current->link;
    	}
    The !found in the while condition should take care of that, no need to break.

  5. #5
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    Oh, but I just realized, you need to remove one of the equals signs from:
    Code:
    		found==true;

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