package rebelsky.exam2;

import java.util.Comparator;

/**
 * Something that knows how to do binary search on arrays using a
 * specified comparator.
 *
 * @author Samuel A. Rebelsky
 * @author YOUR NAME HERE
 */
public class BS 
{
// +--------+--------------------------------------------------
// | Fields |
// +--------+

	/** 
	 * The comparator used to determine the order of
	 * elements in an array.
	 */
	Comparator metric;

// +--------------+--------------------------------------------
// | Constructors |
// +--------------+

	/**
	 * Build a new searcher that uses a particular
	 * comparator.
	 */
	public BS(Comparator _metric)
	{
		this.metric = _metric;
	} // BS(Comparator)


// +----------------+------------------------------------------
// | Public Methods |
// +----------------+

	/**
	 * WRITE ME!
	 */
	public int binarySearch(Object findMe, Object[] stuff)
		throws Exception
	{
		int lb = 0;	// The lower-bound of the portion of interest
		int ub = stuff.length - 1;	// The upper-bound
		while (lb <= ub) {
			int mid = (lb + ub)/2;
			int c = metric.compare(findMe, stuff[mid]);
			if (c == 0) // Found it!
				return mid;
			else if (c < 0)  // Middle element too big!
				ub = mid-1;
			else // Middle element too small!
				lb = mid+1;
		} // while
		// Whoops, doesn't seem to be there
		throw new Exception("Not found!");
	} // binarySearch(Object)

} // class BS