Algs4-2.1.29希尔排序的递增序列

Posted 2021-01-15 longjin2018

2.1.29希尔排序的递增序列。通过实验比较算法2.3中所使用的递增序列和递增序列1,5,19,41,109,209,505,929,2161,3905,8929,16001,36289,64769,146305,260609（这是通过序列9*4^k-9*2^k+1和4^k-3*2^k+1综合得到的)。可以参考练习2.1.11。2.3节中前16个序列为1,4,13,40,121,364,1093,3280,9841,29524,88573,265720,797161,2391484,7174453,21523360
试验结果：不同的序列对相同元素个数与相同元素值的数组排序时，用时会不同。

public class Shell2
{
    public static void sort1(Comparable[] a)
    {
        int N=a.length;
        int[] SN={1,4,13,40,121,364,1093,3280,9841,29524,88573,265720,797161,2391484,7174453,21523360};
        int h;
        for (int hIndex=SN.length-1;hIndex>0;hIndex--)
        {
            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);
            }
        }
    }
   
    public static void sort2(Comparable[] a)
    {
        int N=a.length;
        int[] SN={1,5,19,41,109,209,505,929,2161,3905,8929,16001,36289,64769,146305,260609};
        int h;
        for (int hIndex=SN.length-1;hIndex>0;hIndex--)
        {
            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;
    }
   
  
}

public class SortCompare
{
  
    public static double time (String alg,Double[] a)
    {
        Stopwatch timer =new Stopwatch();
        if(alg.equals("Insertion")) Insertion.sort(a);
        //exercise2.1.24
        if(alg.equals("Insertion2")) Insertion2.sort(a);
        //exercise2.1.25
        if(alg.equals("Insertion3")) Insertion3.sort(a);
        //exercise2.1.26
        if(alg.equals("Insertion4")) Insertion3.sort(a);
        if(alg.equals("Selection")) Selection.sort(a);
        if(alg.equals("Shell1")) Shell2.sort1(a);
        if(alg.equals("Shell2")) Shell2.sort2(a);
       // if(alg.equals("Merge")) Merge.sort(a);
      //  if(alg.equals("Quick")) Quick.sort(a);
      //  if(alg.equals("Heap")) Heap.sort(a);
        return timer.elapsedTime();
    }
   
    public static double timeRandomInput(String alg,int N,int T)
    {
        double total =0.0;
        Double[] a=new Double[N];
        for (int t=0;t<T;t++)
        {
            for (int i=0;i<N;i++)
                a[i]=StdRandom.uniform();
            total+=time(alg,a);
        }
        return total;
    }//end timeRandomInput


   
    public static void main(String[] args)
    {
        /*
        String alg1=args[0];
        String alg2=args[1];
        int N=Integer.parseInt(args[2]);
        int T=Integer.parseInt(args[3]);
        double t1=timeRandomInput(alg1,N,T);
        double t2=timeRandomInput(alg2,N,T);
        StdOut.printf("For %d random Doubles %s is",N,alg1);
        StdOut.printf(" %.2f times faster than %s ",t2/t1,alg2);
        */
        double prevT1=0.0;
        double prevT2=0.0;
        double prevT3=0.0;
        double thisT1=0.0;
        double thisT2=0.0;
        double thisT3=0.0;
        for (int i=128;i<1000000000;i=2*i)
        {
         prevT1=thisT1;
         prevT2=thisT2;
         prevT3=thisT3;
          //
         Double[] a=new Double[i];
         Double[] aCopy=new Double[i];
         for (int j=0;j<i;j++)
           {
               a[j]=StdRandom.uniform();
               aCopy[j]=a[j];
           }
          //
         thisT1=time("Shell1",a);
         thisT2=time("Shell2",aCopy);
         //thisT3=timeRandomInput("Shell",i,1);
         //
        StdOut.printf("---For %d random Doubles ",i);
        StdOut.printf("Shell 1 4 13 40... use time=%.2f ,tihisTime/prevTime=%.2f ",thisT1,thisT1/prevT1);
        StdOut.printf("Shell 1,5,19,41... use time=%.2f ,tihisTime/prevTime=%.2f ",thisT2,thisT2/prevT2);
        StdOut.printf("SN(1,4,13,40...) use time/(1,5,19,41...) use time=%.2f ",thisT1/thisT2);
       // StdOut.printf("Shell     use time=%.2f ,tihisTime/prevTime=%.2f ",thisT3,thisT3/prevT3);
        }
    }
   
}