animalChallengev2.java

package challenge;

import java.util.HashMap;


/**
 * You have 10,000/= bob, and you need to buy exactly 100 animals:
 * - cows 		@1000/-
 * - pigs 		@200/-
 * - chicken 	@50/-
 *
 * 1. You must have at least one of each animal
 * 2. You must use up all Ksh. 10K
 * 3. You must buy exactly 100 animals
 *
 * How many animals can be bought

 Equations
 * x + y + z = 100
 * 1000x + 200y + 50z = 10000
 *
 *
 */

public class AnimalChallenge {

    private static void calc(int[] prices, int[] animals, int totalCost, int totalAnimals){
        HashMap coefficients = getCoefficients(prices[0], prices[1], prices[2], totalCost, animals[0],animals[1], animals[2], totalAnimals);

        int numberOfCows;
        int numberOfPigs = 0;
        int numberOfChicken = 0;

        int x = (int) coefficients.get("x");
        int y = (int) coefficients.get("y");
        int c = (int) coefficients.get("c");

        // loop through the possible values of the eliminated variable while using the created functions
        // to compute the other values and test whether they pass the given condition
        for(numberOfCows = 1; numberOfCows <totalCost/prices[0]; numberOfCows++){
            numberOfPigs = getY(x, y, c, numberOfCows);
            numberOfChicken = getZ(animals[0], animals[1], animals[2], totalAnimals, x, y, c, numberOfCows);

            int totalNoOfAnimals = numberOfCows + numberOfPigs + numberOfChicken;
            int totalPriceOfAnimals = numberOfCows * prices[0] + numberOfPigs * prices[1] + numberOfChicken * prices[2];

            if(totalNoOfAnimals == totalAnimals && totalPriceOfAnimals == totalCost){
                break;
            }
        }
        System.out.println("Number of Cows: "+ numberOfCows);
        System.out.println("Number of Pigs: "+ numberOfPigs);
        System.out.println("Number of Chicken: "+ numberOfChicken);
    }

    private static HashMap<String, Integer> getCoefficients(int x1, int y1, int z1, int c1, int x2, int y2, int z2, int c2){

        HashMap<String , Integer> coefficients = new HashMap<>();
        int xValue = z2 * x1 - z1 * x2;
        int yValue = z2 * y1 - z1 * y2;
        int cValue = z2 * c1 - z1 * c2;
        coefficients.put("x", xValue);
        coefficients.put("y", yValue);
        coefficients.put("c", cValue);

        return coefficients;
    }

    // compute the value of Y for a given value of the eliminated variable
    private static int getY(int x, int y, int c, int a){
        return (c-x*a)/y;
    }

    // compute the value of Z for a given value of the eliminated variable
    private static int getZ(int x1, int y1, int z1, int c1, int x, int y, int c, int a){
        return (c1 * y - c * y1 + y1 * a * x - x1 * a * y) / (z1 * y);
    }

    public static void main(String[] args){
        int[] animalPrices = {1000, 200, 50};
        int[] animalNames = {1, 1, 1};
        int totalCost = 10000;
        int totalAnimals = 100;

        calc(animalPrices, animalNames, totalCost, totalAnimals);
    }
}

Number of Cows: 1
Number of Pigs: 27
Number of Chicken: 72