BinarySearchRecursive.java

/*
Copyright (C) Deepali Srivastava - All Rights Reserved
This code is part of DSA course available on CourseGalaxy.com    
*/

import java.util.Scanner;

public class BinarySearchRecursive 
{
	private BinarySearchRecursive(){} //this class is not for instantiation
	
	public static int search(int[] a, int n, int searchValue) 
	{
		return search(a, 0, n-1, searchValue);
		
	}
	
	public static int search(int[] a, int first, int last, int searchValue)
	{
		if(first>last)
			return -1;
		
		int mid = (first+last)/2;
		
		if(searchValue > a[mid]) 			/*Search in right half */
			return search(a,mid+1,last,searchValue);
		else if(searchValue < a[mid])		/*Search in left half */
			return search(a,first,mid-1,searchValue);
		else
			return mid;
	}
	
	public static void main(String[] args)
	{
		int i,n,searchValue, index;
		
        int[] a = new int[100];

        Scanner scan = new Scanner(System.in);	
        
        System.out.print("Enter the number of elements : ");
        n = scan.nextInt();

        System.out.println("Enter the elements in sorted order  - ");
	    for(i=0; i<n; i++)
            a[i] = scan.nextInt();

	    System.out.print("Enter the search value : ");
        searchValue = scan.nextInt();
	
	    index = search(a, n, searchValue);
	
	    if( index == -1 )
	    	System.out.println("Value " + searchValue + " not present in the array");
	    else
	    	System.out.println("Value " + searchValue + " present at index " + index);
	}
}