public class BinarySearch
{
	public static void printArray(int[] a)
	{
		System.out.print("\nIndex i:      ");
		for(int i=0; i< a.length; i++)
			System.out.printf("%2d, ", i);

		System.out.print("\nElement a[i]: ");
		for(int i=0; i< a.length; i++)
			System.out.printf("%2d, ", a[i]);
			
		System.out.println("\n\n");
	}

	public static void main(String[] args)
	{
		int[] a= { 4, 7, 8, 10, 14, 21, 22, 36, 62, 77, 81, 91};

		// Print the array		
		printArray(a);
		
		// Search for the target using Binary Search
		// We assume that the array is already sorted in increasing order

		int target = 22;
		//int target = 72; // Try this target next

		int idx=-1; // if the target is found its index is stored here
		
		// initial values for the three search varaibles
		int first=0;
		int last= a.length-1; 
		int mid= (first + last)/2;

		while(last >= first)
		{
			
			if( a[mid] == target)
			{
				idx=mid;  // Found it!
				break;    // exit the while loop 
			} 
			else if(a[mid] > target)
			{
				// don't search in a[mid] ... a[last]
				last = mid-1;
			}
			else
			{
				// don't search in a[first] ... a[mid]
				first = mid +1;
			}
		
			// recalculate mid for the next iteration	
			mid = (first + last)/2; // integer division!
		
		} // end of while loop
	
		if(idx == -1)
			System.out.println("Target not found.");
		else
			System.out.println("Target found at index: " + idx);
	}
}