Algs4-2.1.11希尔排序序列改为存数组

Posted 2021-01-15 longjin2018

2.1.11将希尔排序中实时计算递增序列改为预先计算并存储在一个数组中。
public class Shell2
{
    public static void sort(Comparable[] a)
    {
        int N=a.length;
        int h=1;
        int[] SN=new int[20];
        int hMaxIndex=0;
        while (h<N/3)
        {
           SN[hMaxIndex]=h;
            h=3*h+1;
            hMaxIndex++;
        }

       
        for (int hIndex=hMaxIndex;hIndex>0;hMaxIndex--)
        {
            h=SN[hIndex];
            for (int i=h;i<N;i++)
            {
                for (int j=i;j>=h && less(a[j],a[j-h]);j-=h)
                    exch(a,j,j-h);
            }
        }
    }
   
    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;
    }
   
  
}