三向切分的快速排序和優化

壹頁書發表於2016-09-22
排序優化


  1. public class Sort{
  2.     public static void main(String[] args){
  3.         Integer[] data={100,20,21,28,22,26,80,33,3,2,9,8,7,10,77,66,99,96,91,94};
  4.         BaseSort s=new Quick3Way(data);

  6.         s.show(data);

  8.         System.out.println(s.isSorted(data));
  9.     }
  10. }



  14. class Quick3Way extends BaseSort{
  15.     public Quick3Way(Comparable[] data){
  16.         sort(data,0,data.length-1);
  17.     }

  19.     @Override
  20.     void sort(Comparable[] data, int lo, int hi) {
  21.         if(hi<=lo){
  22.             return;
  23.         }
  24.         int lt=lo,i=lo+1,gt=hi;
  25.         Comparable v=data[lo];
  26.         while(i<=gt){
  27.             int cmp=data[i].compareTo(v);
  28.             if(cmp<0) {
  29.                 exch(data, lt++, i++);
  30.             }else if(cmp>0){
  31.                 exch(data,i,gt--);
  32.             }else{
  33.                 i++;
  34.             }
  35.         }
  36.         sort(data,lo,lt-1);
  37.         sort(data,gt+1,hi);
  38.     }
  39. }
  40. abstract class BaseSort {
  41.     abstract void sort(Comparable[] data,int lo,int hi);

  43.     //比較
  44.     public boolean less(Comparable v,Comparable w){
  45.         return v.compareTo(w)<0;
  46.     }

  48.     //列印
  49.     public void show(Comparable[] data){
  50.         for(int i=0;i<data.length;i++){
  51.             System.out.print(data[i]+" ");
  52.         }
  53.         System.out.println("");
  54.     }

  56.     //驗證
  57.     public boolean isSorted(Comparable[] data){
  58.         for(int i=1;i< data.length;i++){
  59.             if(less(data[i],data[i-1]) )
  60.                 return false;
  61.         }
  62.         return true;
  63.     }

  65.     //交換
  66.     public void exch(Comparable[] data,int i,int j){
  67.         Comparable t=data[i];
  68.         data[i]=data[j];
  69.         data[j]=t;
  70.     }
  71. } 

if(hi<=lo){ return; }
小陣列可以改為插入排序。
int M=5;  if(hi<=lo+M){
    Insertion.sort(data,lo,hi);  return;  }

來自 “ ITPUB部落格 ” ，連結：http://blog.itpub.net/29254281/viewspace-2125329/，如需轉載，請註明出處，否則將追究法律責任。

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