Колоквиумска АПС - Сума на два големи броеви (Листи)

import java.util.Scanner;

class DLLNode<E> {
    protected E element;
    protected DLLNode<E> pred, succ;

    public DLLNode(E elem, DLLNode<E> pred, DLLNode<E> succ) {
        this.element = elem;
        this.pred = pred;
        this.succ = succ;
    }

    @Override
    public String toString() {
        return element.toString();
    }
}


class DLL<E> {
    private DLLNode<E> first, last;

    public DLL() {
        // Construct an empty SLL
        this.first = null;
        this.last = null;
    }

    public void deleteList() {
        first = null;
        last = null;
    }

    public int length() {
        int ret;
        if (first != null) {
            DLLNode<E> tmp = first;
            ret = 1;
            while (tmp.succ != null) {
                tmp = tmp.succ;
                ret++;
            }
            return ret;
        } else
            return 0;

    }

    public DLLNode<E> find(E o) {
        if (first != null) {
            DLLNode<E> tmp = first;
            while (tmp.element != o && tmp.succ != null)
                tmp = tmp.succ;
            if (tmp.element == o) {
                return tmp;
            } else {
                System.out.println("Elementot ne postoi vo listata");
            }
        } else {
            System.out.println("Listata e prazna");
        }
        return first;
    }

    public void insertFirst(E o) {
        DLLNode<E> ins = new DLLNode<E>(o, null, first);
        if (first == null)
            last = ins;
        else
            first.pred = ins;
        first = ins;
    }

    public void insertLast(E o) {
        if (first == null)
            insertFirst(o);
        else {
            DLLNode<E> ins = new DLLNode<E>(o, last, null);
            last.succ = ins;
            last = ins;
        }
    }

    public void insertAfter(E o, DLLNode<E> after) {
        if(after==last){
            insertLast(o);
            return;
        }
        DLLNode<E> ins = new DLLNode<E>(o, after, after.succ);
        after.succ.pred = ins;
        after.succ = ins;
    }

    public void insertBefore(E o, DLLNode<E> before) {
        if(before == first){
            insertFirst(o);
            return;
        }
        DLLNode<E> ins = new DLLNode<E>(o, before.pred, before);
        before.pred.succ = ins;
        before.pred = ins;
    }

    public E deleteFirst() {
        if (first != null) {
            DLLNode<E> tmp = first;
            first = first.succ;
            if (first != null) first.pred = null;
            if (first == null)
                last = null;
            return tmp.element;
        } else
            return null;
    }

    public E deleteLast() {
        if (first != null) {
            if (first.succ == null)
                return deleteFirst();
            else {
                DLLNode<E> tmp = last;
                last = last.pred;
                last.succ = null;
                return tmp.element;
            }
        }
        // else throw Exception
        return null;
    }

    public E delete(DLLNode<E> node) {
        if(node==first){
            deleteFirst();
            return node.element;
        }
        if(node==last){
            deleteLast();
            return node.element;
        }
        node.pred.succ = node.succ;
        node.succ.pred = node.pred;
        return node.element;

    }

    @Override
    public String toString() {
        String ret = new String();
        if (first != null) {
            DLLNode<E> tmp = first;
            ret += tmp;
            while (tmp.succ != null) {
                tmp = tmp.succ;
                ret += tmp;
            }
        } else
            ret = "Prazna lista!!!";
        return ret;
    }

    public String toStringR() {
        String ret = new String();
        if (last != null) {
            DLLNode<E> tmp = last;
            ret += tmp + "<->";
            while (tmp.pred != null) {
                tmp = tmp.pred;
                ret += tmp + "<->";
            }
        } else
            ret = "Prazna lista!!!";
        return ret;
    }

    public DLLNode<E> getFirst() {
        return first;
    }

    public DLLNode<E> getLast() {

        return last;
    }

    public void izvadiDupliIPrebroj(){

    }
}
public class BigNumbers {

    public static void calculate(DLL<Integer> lista1, DLL<Integer> lista2)
    {
        DLLNode<Integer> tmp1 = lista1.getFirst();
        DLLNode<Integer> tmp2 = lista2.getFirst();

        DLL<Integer> lista = new DLL<Integer>();

        int sum=0;
        int prva=0;


        while(tmp1!=null && tmp2!=null)
        {
            sum=0;
            sum = tmp1.element + tmp2.element + prva;

            if(sum>9)
            {
                int posledna=0;
                prva=0;

                prva=sum/10;
                posledna=sum%10;

                lista.insertFirst(posledna);
                if(tmp1.succ!=null) tmp1=tmp1.succ;
                else break;
                if(tmp2.succ!=null) tmp2=tmp2.succ;
                else break;

            }

            else
            {
                lista.insertFirst(sum);
                prva=0;
                if(tmp1.succ!=null) tmp1=tmp1.succ;
                else break;
                if(tmp2.succ!=null) tmp2=tmp2.succ;
                else break;
            }

        }





        if(tmp1.succ!=null)  //go dodadov succ
        {

            while(tmp1!=null)
            {


                if(prva==0)
                {
                    lista.insertFirst(tmp1.element);
                    if(tmp1.succ!=null) tmp1=tmp1.succ;
                    else break;

                }
               else {
                if(tmp1.element + prva >9)
                {
                    int posledna=0;
                    //prva=0; //neee

                    prva=(tmp1.element + prva)/10;
                    posledna=(tmp1.element + prva)%10;

                    lista.insertFirst(posledna);
                    if(tmp1.succ!=null) tmp1=tmp1.succ;
                    else break;



                }

                else
                {
                    lista.insertFirst(tmp1.element + prva);
                    prva=0;
                    if(tmp1.succ!=null) tmp1=tmp1.succ;
                    else break;


                }

            }

            }

        }

        if(tmp2.succ!=null)   //go dodadov succ
        {
            tmp2=tmp2.succ; //i ova, zoshto ako prvata e pokratka, ovoj node nema da se stavi na negoviot succ
            while(tmp2!=null)
            {

                if(prva==0)
                {
                    lista.insertFirst(tmp2.element);
                    if(tmp2.succ!=null) tmp2=tmp2.succ;
                    else break;

                }
               else {
                if(tmp2.element + prva >9)
                {
                    int posledna=0;
                    //prva=0; //neee

                    prva=(tmp2.element + prva)/10;
                    posledna=(tmp2.element + prva)%10;

                    lista.insertFirst(posledna);
                    if(tmp2.succ!=null) tmp2=tmp2.succ;
                    else break;


                }

                else
                {
                    lista.insertFirst(tmp2.element + prva);
                    prva=0;
                    if(tmp2.succ!=null) tmp2=tmp2.succ;
                    else break;

                }
            }


            }


        }





        if(prva!=0) lista.insertFirst(1); //go dodadov ovoj red

        System.out.println(lista.toString());


    }

    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);

        String prv = scan.nextLine();
        String vtor = scan.nextLine();

        DLL<Integer> lista1 = new DLL<Integer>();
        DLL<Integer> lista2 = new DLL<Integer>();

        char [] cifri1 = prv.toCharArray();
        char [] cifri2 = vtor.toCharArray();

        for(int i=0; i<cifri1.length; i++)
        {
            lista1.insertFirst(cifri1[i] - '0');;

        }

        for(int i=0; i<cifri2.length; i++)
        {

            lista2.insertFirst(cifri2[i] - '0');;
        }



        calculate(lista1, lista2);

    }

}