CODEWITHSUNDEEP
c++visual-studio-2012
gameboy1995
gameboy1995

Reputation: 13

Doubly Linked List Destructor

I am working on a program that uses doubly linked lists yet my destructor causes an error. I am not sure why this is occurring so an explanation would be great as well as possible steps for a solution.

~GroceryList()
    {
        ItemType *before=head, *current=head, *after=head;
        for(int i=0; i<itemCount; i++)
        {
            before=current;
            current=current->next;
            after=current->next;
            before->next=after;
            after->prev=before;
            delete current;
        }
        current=before=after=NULL;
    };

Upvotes: 2

Views: 1781

Answers (2)

R Sahu
R Sahu

Reputation: 206567

You have a logic error.

for(int i=0; i<itemCount; i++)
{
    before=current;
    current=current->next; 
    after=current->next;
    before->next=after;
    after->prev=before;

    // Add some statements to print the conents of
    // before, current, and after here to debug
    // the memory problem.

    delete current;
    current = after;  // Add this line.
}

Upvotes: 0

Rupesh Yadav.
Rupesh Yadav.

Reputation: 904

First of all you should show error msg.
I think below line is creating problem.

for(int i=0; i<itemCount; i++)
        {
    before=current;     //  this one 
    current=current->next;
    after=current->next;
    before->next=after;
    after->prev=before;
    delete current;     // here you are deleting and again using `current` in first statement in loop?
}

Upvotes: 1

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