CODEWITHSUNDEEP
c++circular-list
Julia Rundström
Julia Rundström

Reputation: 35

assignment operator in double directed circular list adding elements in wrong order

I have problem with my assignment operator in my double directed circular list. when I have a list with content and assign another list with content to it the numbers are jumbled up. The input I use is 5 20 10 but when I print my list the output is 5 10 20. My code looks like this:

#ifndef CDDLIST_H
#define CDDLIST_H

template <typename T>
class CircularDoubleDirectedList<T>{
public: 
    static enum direction{ FORWARD, BACKWARD };
    CircularDoubleDirectedList<T>& operator= (const CircularDoubleDirectedList<T>& obj);
    void addAtCurrent(const T& data);

private:
    class Node{
    public:
        T data;
        Node *next;
        Node *previous;

        Node(const T& data){
            this->data = data;
            this->next = nullptr;
            this->previous = nullptr;
        };
        Node(){
            this->data = NULL;
            this->next = nullptr;
            this->previous = nullptr;
        };
        ~Node(){};
    };
    Node *current;
    direction currentDirection;
    int numberOfElements;


};

template <typename T>
CircularDoubleDirectedList<T>& CircularDoubleDirectedList<T>::operator= (const CircularDoubleDirectedList<T>& obj){
    if (this !=&obj){
        this->currentDirection = obj.currentDirection;
        this->current = nullptr;
        this->numberOfElements = 0;
        Node* walker = obj.current;
        for (int i = 0; i < obj.numberOfElements; i++){
            walker = walker->previous;
            addAtCurrent(walker->data);
        }
    }
    return *this;
}
template <typename T>
void CircularDoubleDirectedList<T>::addAtCurrent(const T& data){
    if (this->numberOfElements == 0){
        Node *node = new Node(data);
        this->current = node;
        node->next = node;
        node->previous = node;
        this->numberOfElements++;
    }
    else{
        Node *node = new Node(data);
        node->previous = this->current;
        node->next = this->current->next;
        this->current->next = node;
        this->current = node;
        this->current->next->previous=this->current;
        this->numberOfElements++;
    }

}
#endif

I have tried to use two walkers, changed direction of the walker(s), moved the walker(s) first and added data second, moved one walker backwards and the other forwards, etc.

Upvotes: 1

Views: 180

Answers (1)

Barmar
Barmar

Reputation: 780929

Your assignment code is adding the elements of obj to this in reverse order, because it's stepping through the previous pointers instead of next. Change

walker = walker->previous;

to

walker = walker->next;

Upvotes: 1

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