Question

I am trying to delete all specific key element in my linked list in one function .
that is if linked list has 1 2 2 3 4 4 5 5 8 2 6 32 4 6 7 7 then if I pass the function 2 that function delete all the 2’s in linked list

my linked list is here

class float_list
{
     struct node
    {
        double data;
        struct node *next;
     };
        node *head;
public:

    float_list(void)
    {
        head = nullptr;
    };

    void appendNode(double);
    void print_list();
    void deleteNode(double);

};

now my deleteNode(double is here)

void float_list::deleteNode(double num)
{
    node *nextptr, *previousptr = nullptr;
    nextptr=head;
    if(!head->data){return;}
    if(head->data==num)
    {
        nextptr= head->next;
        delete head; 
        head = nextptr;
    }
    else
        while(nextptr)
        {
            previousptr= nextptr;
            if(nextptr->data==num)
            {
                previousptr->next = nextptr->next;  
                delete nextptr;
                cout<<"I Found the  --> "<<num<<"  is going to be deleted"<<endl;
                nextptr = previousptr; 
                //nextptr = nextptr->next;
            }
            nextptr = nextptr->next;
        }
        delete nextptr;
        delete previousptr;
}

I tried in all different ways but always get accesss violation error . Please give me conceptual and code hints if possible . thanks
the code is in win32 Vs2010 app

Answer 1

What happens after the while loop end. Well, nextptr == NULL. delete NULL == problem.

Try this:

node *previous = nullptr, *current = head, *temp;

while(current){
    temp = current->next;
    if(abs(current->data - num) < MARGIN_OF_ERROR){
        if (previous){
            previous->next = current->next;
        } else {
            head = current->next;
        }
        delete current;
    } else{
        previous = current;
    }
    current = temp;
}