Algs4-2.1.9给出希尔排序的轨迹

Posted 2021-01-15 longjin2018

 2.1.9按照算法2.3所示轨迹的格式给出希尔排序是如何将数组 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：灰底色表示相关元素未互换，黄底色表示相关元素互换。1-sort省略，与插入排序相同。





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 ",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);
    }
  
}