#include <iostream>
using namespace std;

class ChainNode{
    friend class Chain;
    public:
        ChainNode(int element, ChainNode* next);
    private:
        int data;
        ChainNode* link;
};

class Chain{
    public:
        Chain(): first(NULL){}  //empty constructor
        void insertAtBack(const int& value);
        void insertAtFront(const int& value);
        void deletefromBack();
        void deletefromFront();
        void print();
        ~Chain();
    private:
        ChainNode* first;
};


int main(){
    Chain myChain;
    myChain.insertAtBack(50);
    myChain.insertAtBack(60);

    myChain.insertAtFront(10);
    myChain.insertAtFront(20);
    myChain.insertAtFront(30);
    myChain.print();

    myChain.deletefromBack();
    myChain.deletefromBack();
    myChain.deletefromBack();
    myChain.deletefromBack();
    myChain.deletefromBack();
    myChain.deletefromBack();

    myChain.print();

    myChain.insertAtBack(50);
    myChain.insertAtBack(60);

    myChain.insertAtFront(10);
    myChain.insertAtFront(20);
    myChain.insertAtFront(30);
    myChain.print();

    myChain.deletefromFront();
    myChain.print();
    myChain.deletefromFront();
    myChain.print();
    myChain.deletefromFront();
    myChain.print();
    myChain.deletefromFront();
    myChain.print();
    myChain.deletefromFront();
    myChain.print();
    myChain.deletefromFront();
    myChain.print();
}


ChainNode::ChainNode(int element, ChainNode* next): data(0), link(NULL)
{
    data = element;
    link = next;
}

void Chain::insertAtBack(const int& value){
    ChainNode* tmpPtr = new ChainNode(value,0);
    if(first){
        ChainNode* last = first;
        while(last->link != NULL)
            last = last->link;
        last->link = tmpPtr;
    }else{
        first  = tmpPtr;
    }
}
void Chain::insertAtFront(const int& value){
    ChainNode* tmpPtr = new ChainNode(value,0);
    if(first){
        tmpPtr->link = first;
        first = tmpPtr;
    }else{
        first  = tmpPtr;
    }
}
void Chain::deletefromBack(){
    int value;
    // get the mry location of the last node
    if (first){
        ChainNode* last = first;
        while(last->link != NULL){
            last = last->link;
        }// end while


        if(first == last){
            value = last->data;
            delete last;
            first = NULL;
            cout << value << " is removed" << " and nothing remained"<< endl;
        }else{
            ChainNode* previous = first;
            while(previous->link != last){
                previous = previous->link;
            }

            previous->link = NULL;
            value = last->data;
            delete last;
            cout << value << " is removed" << endl;
        }// end inner if
    }else{
        cout << "remove unsuccessful: no nodes remained" << endl;
    }// end if
}
void Chain::deletefromFront(){
    int value;
    // get the mry location of the last node

    if(first){
        ChainNode* tmpPtr = first;
        first = first->link;
        value = tmpPtr->data;
        delete tmpPtr;
        cout << value << " is removed" << endl;
    }else{
        cout << "remove unsuccessful: no nodes remained" << endl;
    }
}
void Chain::print(){
    if(first != NULL){
        ChainNode* tmpPtr = first;
        while(tmpPtr != NULL){
            cout << tmpPtr->data << " ";
            tmpPtr = tmpPtr->link;
        }// end while
        cout << endl;
    }else{
        cout << "nothing" << endl;
    }// end if
}
Chain::~Chain(){

    ChainNode* tmpPtr = first;
    while(tmpPtr != NULL){
        first = first->link;
        delete tmpPtr;
        tmpPtr = first;
    }// end while
}