2.1.9按照算法2.3所示軌跡的格式給出希爾排序是如何將數組 E A S Y S H E L L S O R T Q U E S T I O N排序的。
答：灰底色表示相關元素未互換，黃底色表示相關元素互換。1-sort省略，與插入排序相同。





public class Shell
{
public static void sort(Comparable[] a)
{
int N=a.length;
int h=1;
while (h<N/3) h=3*h+1;
while (h>=1)
{
for (int i=h;i<N;i++)
{
// for (int j=i;j>=h && less(a[j],a[j-h]);j-=h)
for (int j=i;j>=h ;j-=h)
{
if(h>1) StdOut.printf("h=%-5d i=%-5d j=%-5d\n",h,i,j);
if( less(a[j],a[j-h])) exch(a,j,j-h);
}
}
h=h/3;
}
}

private static boolean less(Comparable v,Comparable w)
{ return v.compareTo(w)<0;}

private static void exch(Comparable[] a,int i,int j)
{
Comparable t=a[i];
a[i]=a[j];
a[j]=t;
}

private static void show(Comparable[] a)
{
for (int i=0;i<a.length;i++)
StdOut.print(a[i]+" ");
StdOut.println();
}

public static boolean isSorted(Comparable[] a)
{
for (int i=0;i<a.length;i++)
if(less(a[i],a[i-1])) return false;
return true;
}

public static void main(String[] args)
{
String[] a={"E","A","S","Y","S","H","E","L","L","S","O","R","T","Q","U","E","T","I","O","N"};
sort(a);
}

}

Algs4-2.1.9給出希爾排序的軌跡