// Searching.java
// Date: July 23, 2001

public class Searching
{
	// Searches array a for item elt.  If it's found,
	// return the index of elt; otherwise, return -1.
	// This method searches sequentially through the array.
	public static int sequential(int elt, int[] a)
	{
		// Loop from 1 to the length of a minus 1
		for (int i = 0; i < a.length; i++)
		{
		   // For each entry, check if it is the same as elt
		   // If so, return the current index
		 	 if (a[i] == elt)
		 	 {
		 	 		return i;
		 	 }
		}		
		
		// If elt was not found, return -1
		return -1;
	
	}

	// Searches array a for item elt.  If it's found,
	// return the index of elt; otherwise, return -1.
	// This method performs a binary search, and assumes
	// that the input array is sorted in increasing order.
	public static int binary(int elt, int[] a)
	{
		int leftSide = 0;
		int rightSide = a.length-1;
		
		// Loop while left is less than right minus 1. 
		// If this is not true, then we should check to
		// see if the elt is at either endpoint.
		while (leftSide < rightSide-1)
		{
			// Find the index in the middle of left and right
			int midIndex = (rightSide + leftSide)/2;
			// If elt equals the middle value, return the index
			if (elt == a[midIndex])
			{
				return midIndex;
			}
			// If elt is bigger than the middle value,
			// move the left side in
			else if (elt > a[midIndex])
			{
				leftSide = midIndex;
			}
			// Otherwise, move the right side in
			else
			{
				rightSide = midIndex;
			}
		} // end while
		if (elt == a[leftSide])
		{
		  return leftSide;
		}
		else if (elt == a[rightSide])
		{
			return rightSide;
		}
		else
		{
			// If we get to this point, elt must not be in the array
			// so return -1 to indicate its absence.
			return -1;
		}
	}

}