OperationerMedNaturligaHeltal

import java.util.*;

class OperationerMedNaturligaHeltalGivnaSomTeckenStrangar
{
    public static void main(String[] args)
    {
        System.out.println("OPERATIONER MED NATURLIGA HELTAL GIVNA SOM TECKENSTRANGAR\n");

        //mata in tv� naturliga heltal
        Scanner in = new Scanner(System.in);
        System.out.println("tv� naturliga heltal:");
        String tal1 = in.next();
        String tal2 = in.next();
        System.out.println();

        //addera heltalen och visa resultatet
        String summa = addera(tal1, tal2);
        visa(tal1, tal2, summa, '+');

        //subtrahera heltalen och visa resultatet
        String differens = subtrahera(tal1, tal2);
        visa(tal1, tal2, differens, '-');
    }

    //addera tar emot tv� naturliga heltal givna som teckenstr�ngar, och returnerar deras
    //summa som en teckenstr�ng.
    public static String addera(String talet1, String talet2)
    {
        StringBuilder tal1 = new StringBuilder(talet1);
        StringBuilder tal2 = new StringBuilder(talet2);

        if(tal1.length() > tal2.length())
        {
            System.out.println(tal1.length() - tal2.length());
            for(int i = 0; i < (tal1.length() - tal2.length()) + 1; i++)
            {
                tal2.insert(0, 0);
            }
        }
        else if(tal2.length() > tal1.length())
        {
            for(int i = 0; i < (tal2.length() - tal1.length()) + 1; i++)
            {
                tal1.insert(0, 0);
            }
        }

        StringBuilder summa = new StringBuilder();
        int minne = 0;
        int summa_int;

        for(int i = 0; i < tal1.length(); i++)
        {
            summa_int = (tal1.charAt((tal1.length() - 1) - i) - 48) + (tal2.charAt((tal2.length() - 1) - i) - 48) + minne;
            minne = 0;
            if(summa_int >= 10) //Om summan alltså överstiger 9
            {
                summa_int = summa_int - 10;
                minne = 1;
            }

            summa.insert(0, summa_int);

        }

        if(minne == 1)
        summa.insert(0, minne);
        String summaString = summa.toString();

        return summaString;
    }

    //subtrahera tar emot tv� naturliga heltal givna som teckenstr�ngar, och returnerar
    //deras differens som en teckenstr�ng.
    //Det f�rsta heltalet �r inte mindre �n det andra heltalet.
    public static String subtrahera(String talet1, String talet2)
    {
        StringBuilder tal1 = new StringBuilder(talet1);
        StringBuilder tal2 = new StringBuilder(talet2);
        int differens = 0;
        StringBuilder diff = new StringBuilder();
        int minne = 0;

        if(tal1.length() > tal2.length())
        {
            for(int i = 0; i < (tal1.length() - tal2.length()) + 1; i++)
            {
                tal2.insert(0, 0);
            }
        }

        for(int i = 0; i < tal1.length(); i++)
        {
            if(tal1.charAt(tal1.length() - 1 - i) < tal2.charAt(tal2.length() - 1 - i))
            {
                differens = ((tal1.charAt(tal1.length() - 1 - i) - 48) + 10) - (tal2.charAt(tal1.length() - 1 - i) - 48) - minne;
                minne = 1;
            }
            else
            {
                differens = ((tal1.charAt(tal1.length() - 1 - i) - 48)) - (tal2.charAt(tal1.length() - 1 - i) - 48) - minne;
                minne = 0;
            }

            diff.insert(0, differens);
        }

        String differensString = diff.toString();

        return differensString;
    }

    //visa visar tv� givna naturliga heltal, och resultatet av en aritmetisk operation
    //utf�rd i samband med heltalen
    public static void visa(String tal1, String tal2, String resultat, char operator)
    {
        //s�tt en l�mplig l�ngd p� heltalen och resultatet
        int len1 = tal1.length();
        int len2 = tal2.length();
        int len = resultat.length();
        int maxLen = Math.max(Math.max(len1, len2), len);

        tal1 = sattLen(tal1, maxLen - len1);
        tal2 = sattLen(tal2, maxLen - len2);
        resultat = sattLen(resultat, maxLen - len);

        //visa heltalen och resultatet
        System.out.println(" " + tal1);
        System.out.println("" + operator + " " + tal2);
        for(int i = 0; i < maxLen + 2; i++)
            System.out.print("-");
        System.out.println();
        System.out.println(" " + resultat + "\n");
    }

    //sattLen l�gger till ett angivet antal mellanslag i b�rjan av en given str�ng
    public static String sattLen(String s, int antal)
    {
        StringBuilder sb = new StringBuilder(s);
        for(int i = 0; i < antal; i++)
            sb.insert(0, " ");

        return sb.toString();
    }
}