import java.util.Arrays;

public class QuickSort2
{
    /* --------------------------------------------------------
       More efficient way:

		ONLY swap A[low] and A[high] when

                    A[low] > pivot        A[high] < pivot
       --------------------------------------------------------- */
    public static <T extends Comparable<T>> int partition(T[] A, int s, int e) 
    {
	T pivot = A[s];
	
        int low = s+1, high = e-1;

	System.out.println("\npartition(A," + s + "," + e +"):");
	System.out.print("Index --> ");
        for ( int k = 0; k < A.length; k++)
            System.out.print( k + "  ");
	System.out.println();

        while (low < high) 
        {
	    // Show progress
	    System.out.print(">>>>     " + Arrays.toString(A));
	    System.out.print("   Pivot = " + pivot 
			+ " low = " + low + " high = " + high);

	    // Find A[low] > pivot
	    while ( low < high && A[low].compareTo(pivot) <= 0 )
            {
		low++;
            }

	    // Find A[high] < pivot
	    while ( low < high && A[high].compareTo(pivot) >= 0 )
            {
		high--;
            }

	    // Swap A[low] and A[high]
	    if ( low < high )
	    {
                System.out.println("  A[" + low + "] <-->  " + " A[" + high + "]");
		exch(A, low, high);
		low++;
		high--;
	    }

        }

	// Show progress
	System.out.print(">>>>     " + Arrays.toString(A));
	System.out.print("   Pivot = " + pivot 
			+ " low = " + low + " high = " + high);
        System.out.println(" ** exch pivot A[" + s + "] and A[" + high + "]");

	exch(A, s, high);

	System.out.print("Output:  " + Arrays.toString(A));
        System.out.println("\n");

	return high;
    }

    public static <T extends Comparable<T>> void exch(T[] A, int i, int j)
    {
        T h = A[i];
	A[i] = A[j];
	A[j] = h;
    }
}