// Source code example for "A Practical Introduction
// to Data Structures and Algorithm Analysis"
// by Clifford A. Shaffer, Prentice Hall, 1998.
// Copyright 1998 by Clifford A. Shaffer

import java.io.*;

// Driver class for binary search routine
class Bsearchmain {
  static final int UNSUCCESSFUL = -1;

// Perform a binary search in array for the element with
// key value K.  left and right are the left and right bounds,
// respectively, of the part of the array to be searched.
static int binary(int K, int[] array, int left, int right) {
  // Return position of the element in array (if any) with value K
  int l = left-1;
  int r = right+1;     // l and r are beyond the bounds of array
  while (l+1 != r) {   // Stop when l and r meet
    int i = (l+r)/2;   // Look at middle of remaining subarray
    if (K < array[i]) r = i;     // In left half
    if (K == array[i]) return i; // Found it
    if (K > array[i]) l = i;     // In right half
  }
  return UNSUCCESSFUL; // Search value not in array
}
	
  // Main routine for binary search driver
  public static void main(String args[]) throws IOException {
    Assert.notFalse(args.length == 2, "Usage: Bsearchmain <size> <key>");
    int size = Integer.parseInt(args[0]);
    int K = Integer.parseInt(args[1]);

    int[] A = new int[size];

    // Not a particularly exciting test case
    for (int i=0; i<size; i++)
      A[i] = i;

	System.out.println("For an array of size " + size +
	                   " a binary search for key " + K +
					   " returns " + binary(K, A, 0, size-1));
    System.in.read();
  }

}