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Thread: Rational - GCD issue

  1. #1
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    Default Rational - GCD issue

    Hello, I am having trouble trying to build the "gcd(Greatest common divisor". It's where if I input "1/2 - 3/4" output would be "-2/8", where I would want "-1/4". Here is my code. I finished all my arithmetic's, and now all I need to do is simplify my answers. After that, I should be good with this code. Any help is appreciated.

    import java.util.Scanner;
     
     
    public class Rational {
     
     
      // TODO Auto-generated method stub
      //Data members
       private int numerator;
       private int denominator;
      //Constructors
      Rational()
      { 
     
       numerator = 0;
       denominator = 1;
      }
     
      Rational(int num, int den)
      {
     
       numerator = num;
       denominator = den;
      }
     //Accessors
      public int getNumerator()
      {
       return numerator;
      }
      public int getDenominator()
      {
       return denominator;
      }
      // Modifiers
      public void setNumerator(int num)
      {
       numerator = num;
      }
      public void setDenominator(int den)
      {
       denominator = den;
      }
      public Rational inputRational(){
      Scanner input = new Scanner(System.in);
      System.out.println("Enter numerator");
      numerator = input.nextInt();
      System.out.println("Enter Denominator");
      denominator = input.nextInt();
      return new Rational(numerator, denominator);
     
     }
     public String toString()
     {
      return numerator + "/" + denominator;
     }
     private static int gcd(int m, int n)
        {
            int r;
            while(n!= 0)
            {
                r = m % n;
                m = n;
                n = r;     
                }
            return m;
            }
     
     //Adding
     public Rational add(Rational f)
     {
      int num;
      int den;
      num = (numerator * f.denominator) + (f.numerator * denominator);
      den = denominator * f.denominator;
      return new Rational(num, den);
     }
     public void sub(Rational f1, Rational f2)
     {
      numerator = (f1.numerator * f2.denominator) - (f2.numerator * f1.denominator);
      denominator = f1.denominator * f2.denominator;
     
     }
     public Rational mul(Rational f)
     {
      int num;
      int den;
      num = numerator * f.numerator;
      den = denominator * f.denominator;
      return new Rational(num, den);
     }
     public void div(Rational f1, Rational f2)
     {
      this.numerator = f1.numerator * f2.denominator;
      this.denominator = f1.denominator * f2.numerator;
     }
     public static double divided(Rational f1, Rational f2)
     {
      double value;
      value = (f1.numerator/f2.denominator)*(f2.denominator/f2.numerator);
      return value;
      }
     }

    Here's my tester.
    public class TestRational {
     
     public static void main(String[] args) {
      // TODO Auto-generated method stub
      Rational f1 = new Rational();
      Rational f2 = new Rational();
      Rational f3 = new Rational();
      f1.inputRational();
      f2.inputRational();
     
      f3 = f1.add(f2);
      System.out.println(f1.toString() + " + " + f2.toString() + " = " + f3.toString());
     
      f3.sub(f1,f2);
      System.out.println(f1.toString() + " - " + f2.toString() + " = " + f3.toString());
     
      f3 = f1.mul(f2);
      System.out.println(f1.toString() + " * " + f2.toString() + " = " + f3.toString());
     
      f3.div(f1, f2);
      System.out.println(f1.toString() + " / " + f2.toString() + " = " + f3.toString());
     
      System.out.println(Rational.divided(f1,f2));
      f1.setNumerator(2);
      f2.setDenominator(5);
      System.out.println("Numerator: " +f1.getNumerator());
      System.out.println("Denominator: "+f2.getDenominator());
     }
     
    }


  2. #2
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    Default Re: Rational - GCD issue

    This is a time when posting an example run would be helpful to explain what you're asking for help with. So when I run your code for the fractions you suggest, I get:
    Enter numerator
    1
    Enter Denominator
    2
    Enter numerator
    3
    Enter Denominator
    4
    1/2 + 3/4 = 10/8
    1/2 - 3/4 = -2/8
    1/2 * 3/4 = 3/8
    1/2 / 3/4 = 4/6
    0.0
    Numerator: 2
    Denominator: 5
    Are you asking for help to simplify all of the resulting fractions, 10/8, -2/8, 3/8, and 4/6?

    What are the results 0.0, Numerator: 2 and Denominator: 5 supposed to be? Are those right?

    I notice that you never use the method gcd(). Why is that?

  3. #3
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    Default Re: Rational - GCD issue

    Quote Originally Posted by GregBrannon View Post
    This is a time when posting an example run would be helpful to explain what you're asking for help with. So when I run your code for the fractions you suggest, I get:
    Enter numerator
    1
    Enter Denominator
    2
    Enter numerator
    3
    Enter Denominator
    4
    1/2 + 3/4 = 10/8
    1/2 - 3/4 = -2/8
    1/2 * 3/4 = 3/8
    1/2 / 3/4 = 4/6
    0.0
    Numerator: 2
    Denominator: 5
    Are you asking for help to simplify all of the resulting fractions, 10/8, -2/8, 3/8, and 4/6?

    What are the results 0.0, Numerator: 2 and Denominator: 5 supposed to be? Are those right?

    I notice that you never use the method gcd(). Why is that?
    Thanks for the reply. Yes, I was missing the method gcd. Here is what i've done.

    int divisor = gcd(numerator, denominator);
    numerator = numerator/divisor;
    denominator = denominator/divisor;

    ^this should be posted right after the add/sub/mul/div parts. It works for Sub/Div.

    if (numerator == 0){
    return "0";
    }
    else if (numerator == denominator){
    return "1";

    ^I put this in the ToString method. So, yeah, just figuring out whats wrong with simplifying the addition & Multiplication, and i'm finish with this work.

  4. #4
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    Default Re: Rational - GCD issue

    Hello.
    You are still fine.
    Suppose your output is n/m. You can find the common factors for n and m one by one. If a factor say 'f' is found then reduce both n and m by f. With this you can avoid GCD.

    Syed.

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