随机化快速排序

#include<iostream>
 #include<vector>
 #include<iterator>
 #include<algorithm>
 #include<time.h>
 using namespace std;
template<class T>
 class CMP //抽象操作符类
 {
  public:
   virtual bool operator()(const T&one,const T&other)=0; //纯虚函数,重载操作符()
 };
template<class T>
 class LessThan:public CMP<T> //小于操作符类
 {
  public:
   bool operator()(const T&one,const T&other)
   {
    return one<other;
   }
 };
template<class T>
 class GreatThan:public CMP<T>
 {
  public:
   bool operator()(const T&one,const T&other)
   {
    return one>other;
   }
 };
template<class Iterator,class T> //待排序元素的类型
 class Sort //抽象排序类
 {
  protected:
   Iterator array; //指向待排序区间的开始指针
  public:
   virtual void operator()(const Iterator &beg,const Iterator &end,CMP<T> &cmp)=0;
 };
template<class Iterator,class T> 
 class QuickSort:public Sort<Iterator,T>
 {
  private:
   int low,high; //指向待排序区间开始和结束
   int Partition(int low,int high,CMP<T>&cmp); //将区间[low...high]划分成[low...pivot],[pivot+1...high]
   int RandPos(int low,int high); //在low...high之间返回一个随机的位置
   void Exchange(int i,int j); //交换位置i和位置j的两个元素
   void Sort_Function(int low,int high,CMP<T>&cmp); //将区间[low...high]归并排序
  public:
   void operator()(const Iterator &beg,const Iterator &end,CMP<T> &cmp)
   {
    low=0;
    high=end-beg-1;
    array=beg;
    Sort_Function(low,high,cmp);
   }
 };
template<class Iterator,class T>
 int QuickSort<Iterator,T>::RandPos(int low,int high)
 {
  int n=high-low+1;
  srand((unsigned)time(0));
  int offset=rand()%n;
  if(offset==n) offset--;
  int pos=low+offset;
  if(pos<=high && pos>=low) return pos;
  else return low;
 }
template<class Iterator,class T>
 void QuickSort<Iterator,T>::Exchange(int i,int j)
 {
  T tmp;
  tmp=array[i];
  array[i]=array[j];
  array[i]=tmp;
 }
template<class Iterator,class T>
 int QuickSort<Iterator,T>::Partition(int low,int high,CMP<T> &cmp)
 {
  int pos=RandPos(low,high); 
  Exchange(low,pos);
  int i,j;
  i=low;
  j=high;
  T tmp=array[low];
  while(i<j)
  {
   while(i<j && array[j]>tmp) j--;
   if(i<j) array[i++]=array[j];
   while(i<j && array[i]<tmp) i++;
   if(i<j) array[j--]=array[i];
  }
  array[i]=tmp;
  return i;
 }
template<class Iterator,class T>
 void QuickSort<Iterator,T>::Sort_Function(int low,int high,CMP<T> &cmp)
 {
  if(low<high)
  {
   int pivot=Partition(low,high,cmp);
   Sort_Function(low,pivot-1,cmp);
   Sort_Function(pivot+1,high,cmp);
  }
 }
 template<class Iterator,class T>
 void Quick_Sort(const Iterator &beg,const Iterator &end,CMP<T>&cmp)
 {
  QuickSort<Iterator,T> ms;
  ms(beg,end,cmp);
 }
void main()
 {
  vector<int>a;
  srand((unsigned)time(0));
  const int n=88;
  int x;
  for(int i=0;i<n;i++) 
  {
   x=rand()%n;
   a.push_back(x);
  }
  Quick_Sort<vector<int>::iterator,int>(a.begin(),a.end(),GreatThan<int>());
  //Merge_Sort<vector<int>::iterator,int>(a.begin(),a.end(),LessThan<int>());
  copy(a.begin(),a.end(),ostream_iterator<int>(cout," "));
  cout<<endl;
 }