Linked List Queue in C++

Question

I apologize that this is a rather long question...I am making a specific function for a linked list implementation of a queue. This function is called int Queue::modify(int item), where it takes in an integer, and if this integer occurs in the queue more than once, I have to delete all occurrences of the integer from the queue except the first one.

So for example, if my queue looks like [1,2,2,2,2,2,3] and the item is 2, the resulting queue would look like [1,2,3]. My code, however, is outputting [1,2,2,2,3].

Below is my code, and below my code, is my explanation on how I tried to implement this:

int Queue::modify(int item){
    node* curr = front;
    node* temp;
    int counter = 0;

    if (curr == NULL){
        return 0;
    }
    //checking to see if first instance of queue is == item
    if (curr->data == item){
        counter++;
    }   

    //checking to see if instances after first instance of queue is == item
    while (curr != NULL){
        if (curr->next != NULL){
            temp = curr->next;
            if (temp->data == item){
                counter ++;
                if (counter > 1){
                    if (curr->next->next != NULL){
                        curr->next = curr->next->next; //I think something is wrong here??
                    }
                    delete temp;
                }               
            }
            curr = curr->next;
        }
        //this is for the last instance of the queue, so curr->next == NULL
        else{
            if (curr->data == item){
                counter++;
                if (counter > 1){
                    delete curr;
                    curr = NULL;
                }
                else
                    curr = curr->next; //so curr should be NULL now
            }
            else
                curr = curr->next; //so curr should be NULL now  
        }
    }
    return counter;
}

So basically, what I tried was having temp = curr->next so that if curr->next->data == item, then I can have curr's next pointer point to the node after temp so that the list is still linked, curr->next = curr->next->next, and then delete temp as shown in the wonderfully illustrated diagram below:

I have a feeling that I'm brain farting and that curr->next = curr->next->next is not correct...thank you in advance for any suggestions on what's wrong with my code! Also, this IS HOMEWORK so although I would absolutely love a full code solution, please refrain from posting full code solutions....thank you! :D

Answer 1

I suppose, that condition

if (curr->next->next != NULL){

not needed. You can make copy

curr->next = curr->next->next; 

in any case

Answer 2

In these lines,

if (counter > 1){
    if (curr->next->next != NULL){
        curr->next = curr->next->next; //I think something is wrong here??
    }

You are skipping nodes. The surrounding code needs to be:

if (temp->data == item)
{
    counter ++;
    if (counter > 1){
       curr = temp->next;
       delete temp;
    }               
}
else
{
   curr = curr->next;
}