Question

I have problem about struct and class. Now I define class inside the struct and then I create the struct as node and push node in queue. The problem is when I pop queue I create the node to receive pop node but the class in node is a new one, not the same as before push. Follow as code.

    struct queueNode {
        Puzzle puzzle;
        queueNode *next;
        short lastMove;
    };

    class Puzzle {

    private :
        short field[4][4];
        short posBlankI;
        short posBlankJ;
    public :
        Puzzle();
        bool isFinish();
        void print();
        void create();
    }

    class Queue {
        private:
            queueNode *first, *last;

        public:
            Queue(){
                first = new queueNode;
                first->next = NULL;
                last = first;
            }
            ~Queue() { delete first; }
            bool isEmpty(){ return (first->next == NULL); }
            void push(queueNode *aux){

                last->next = aux;
                last = aux;

            }
            queueNode pop(){
                queueNode *aux = first;
                first = first->next;
                return *aux;
            }
    };

    //global variable      
    Queue *q = new Queue();

    int main(){
        queueNode *root = new queueNode;
        root->puzzle.create();
        q->push(root);
        q->pop().puzzle.print();
        return 0;
    }

Answer 1

The problem has nothing to do with a class being member of a struct.

The constructor of Queue creates a queue with 1 blank node. q->push(root) inserts the 2nd node at the end. q->pop() returns the copy of the 1st (blank) node, not the 2nd as you expect.