Division of Fractions
by Isai Damier, Android Engineer @ Google

/***************************************************************************
 *  Author: Isai Damier
 * Title: Division of Fractions
 * Project: geekviewpoint
 * Package: algorithms
 *
 * Statement:
 *   Multiplication the two given fractions
 *
 * Sample Input: {-5,6}, {6,8})
 * Sample Output: {-5,8}
 *
 * Technical Details:
 *   This is the same algorithm you learned in grade school:
 *   1) cross multiply the numerators and the denominators
 *   4) reduce the resulting fraction using the GCD (greatest common
 *     divisor) of its numerator and denominator.
 *
 **************************************************************************/ 
 public int[] fractionDivision(int[] a, int[] b) {
  int numerator = a[0] * b[1];
  int denominator = a[1] * b[0];
  int num = 0 > numerator ? -numerator : numerator;
  int den = 0 > denominator ? -denominator : denominator;
  int gcd = GCD(num, den);
  gcd = 0 > gcd ? -gcd : gcd;
  return new int[]{numerator / gcd, denominator / gcd};
}

import org.junit.Test;
import static org.junit.Assert.*;

public class NumbersTest {

  /**
   * Test of fractionDivision method, of class Numbers.
   */
  @Test
  public void testFractionDivision() {
    System.out.println("fractionDivision");
    int[] a = new int[] {8,5};
    int[] b = new int[] {10,15};
    Numbers instance = new Numbers();
    int[] expResult = {12,5};
    int[] result = instance.fractionDivision(a, b);
    assertArrayEquals(expResult, result);

    a = new int[] {5,6};
    b = new int[] {6,8};
    expResult = new int[]{10,9};
    result = instance.fractionDivision(a, b);
    assertArrayEquals(expResult, result);
  }
}