P. 133 Ex. 4

// Shavit Borisov
// CW

import java.util.Scanner;

public class BinarySearch {

    static Scanner in = new Scanner(System.in);

    public static void main(String[] args)
    {
        final int SIZE = 3;
        int[] array = new int[SIZE];
        getData(array);
        int key = -1;

        int currentResult;

        System.out.printf("What is your key? Enter 0 to stop the procedure. ");
        key = in.nextInt();

        while(key != 0)
        {
            currentResult = Bsearch(array, key);
            if(currentResult == -1)
                System.out.printf("Key not found\n");
            else
                System.out.printf("Key found in array[%d]\n", currentResult);

            System.out.printf("What is your next key? ");
            key = in.nextInt();
        }
        in.close();
    }

    private static void getData(int[] array)
    {
        for(int i = 0; i < array.length; i++)
        {
            System.out.printf("Enter value for array[%d]: ", i);
            array[i] = in.nextInt();
        }
    }

    private static int Bsearch(int[] array, int key)
    {
        int middle;
        int low = 0;
        int high = array.length - 1;
        while(low <= high)
        {
            middle = (low + high) / 2;
            if(array[middle] == key)
                return middle;
            else
            {
                if(array[middle] > key)
                    high = middle - 1;
                else
                    low = middle + 1;
            }
        }
        return -1;
    }
}