import SimpleInput;
import SimpleOutput;
import java.lang.Math;

public class SortShell3 {
// a sorting shell for experiments with the refined quicksort

public static void quicksort (int [] a) {
// method to sort using the refined quicksort
    quicksortKernel (a, 0, a.length-1);
}

private static void quicksortKernel (int [] a, int first, int last) {
    int left=first+1;
    int right=last;
    int temp;

    // begin by selecting a random integer, midIndex, between first and last,
    // and then swap a[first] with a[midIndex].
    int midIndex = first + (int)Math.floor((last-first)*Math.random());
    temp = a[first];
    a[first] = a[midIndex];
    a[midIndex] = temp;

    // quicksortKernel continues as in SortShell2
    while (right >= left) {
        // search left to find small array item
        while ((right >= left) && (a[first] <= a[right]))
            right--;
        // search right to find large array item
        while ((right >= left) && (a[first] >= a[left]))
            left++;
        // swap large left item and small right item, if needed
        if (right > left) {
            temp = a[left];
            a[left] = a[right];
            a[right] = temp;
        }
    }
    // put a[first] in its place
    temp = a[first];
    a[first] = a[right];
    a[right] = temp;

    // recursively apply algorithm to a[first]..a[right-1] 
    // and a[right+1]..a[last], provided these segments contain >= 2 items
    if (first < right-1)
        quicksortKernel (a, first, right-1);
    if (right+1 < last)
        quicksortKernel (a, right+1, last);   
}

public static void main (String [] args) {
    // declarations: two arrays and I/O;
    int size = 12;
    int [] c = new int [size];
    int [] d = new int [size];
    SimpleOutput out = new SimpleOutput ();
    SimpleInput  in  = new SimpleInput  ();

    // initial arrays to same values by reading and copying
    out.println ("Please enter " + size + " integer values to sort");
    for (int i = 0; i < size; i++) {
       c[i] = in.readInt();
       d[i] = c[i];
    }

    // sort and print first array
    quicksort (c);
    out.println ("Result of Refined Quicksort:");
    for (int i = 0; i < size; i++) 
        out.print(c[i] + "\t");
    out.println();

} // main
} // SortShell3