The shellSort.java Program
// shellSort.java
// demonstrates shell sort
// to run this program: C>java ShellSortApp
//-------------------------------------------------------------
class ArraySh
{
private double[] theArray; // ref to array theArray
private int nElems; // number of data items
//-------------------------------------------------------------
public ArraySh(int max) // constructor
{
theArray = new double[max]; // create the array
nElems = 0; // no items yet
}
//-------------------------------------------------------------
public void insert(double value) // put element into array
{
theArray[nElems] = value; // insert it
nElems++; // increment size
}
//-------------------------------------------------------------
public void display() // displays array contents
{
System.out.print("A=");
for(int j=0; j<nElems; j++) // for each element,
System.out.print(theArray[j] + " "); // display it
System.out.println(""); }
//-------------------------------------------------------------
public void shellSort()
{
int inner, outer;
double temp;
int h = 1; // find initial value of h
while(h <= nElems/3)
h = h*3 + 1; // (1, 4, 13, 40, 121,...)
while(h>0) // decreasing h, until h=1
{
// h-sort the file
for(outer=h; outer<nElems; outer++)
{
temp = theArray[outer];
inner = outer;
// one subpass (eg 0, 4,8)
while(inner > h-1 && theArray[inner-h] >= temp)
{
theArray[inner] = theArray[inner-h];
//System.out.println("h="+h+"; swarp: "+inner+"/"+(inner-h));
inner -= h;
}
theArray[inner] = temp;
} // end for
h = (h-1) / 3; // decrease h
//display();
} // end while(h>0)
} // end shellSort()
//-------------------------------------------------------------
} // end class ArraySh
////////////////////////////////////////////////////////////////
class ShellSortApp
{
public static void main(String[] args)
{
int maxSize = 50; // array size
ArraySh arr;
arr = new ArraySh(maxSize); // create the array
for(int j=0; j<maxSize; j++) // fill array with
{ // random numbers
double n = (int)(java.lang.Math.random()*99);
arr.insert(n);
}
arr.display(); // display unsorted array
arr.shellSort(); // shell sort the array
arr.display(); // display sorted array
} // end main()
} // end class ShellSortApp