C++随机化快速排序

C++随机化快速排序

// 随机化快速排序.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include<iostream>
#include<ctime>
using namespace std;
double a[100];

int random(int m,int n)            //产生一个随即下标，用其对应的数组元素作为比较标准
{
  srand((unsigned)time(NULL));
  return m + (rand()%(n-m+1));
}

int qartition(double *a,int begin,int end)    //一趟快速排序
{
 
  int i = begin-1,j=begin;
  double x = a[end];
  while(j<end)
  {
   if(a[j]<=x)
   {
    i++;
    double temp = a[i];
    a[i]=a[j];
    a[j]=temp;
   }
   j++;
  }
  double temp = a[end];
  a[end]=a[i+1];
  a[i+1]=temp;
  return i+1;
}
 
int random_qartition(double *a,int begin,int end)    //一趟随机化快速排序
{
   int q = random(begin,end);
   double temp = a[end];
   a[end]=a[q];
   a[q]=temp;
   return qartition(a,begin,end);
}

void random_fast_sort(double *a,int begin,int end)   //随机化快速排序
{
 if(begin<end)
 {
       int p = random_qartition(a,begin,end);
     random_fast_sort(a,begin,p-1);
     random_fast_sort(a,p+1,end);
 }
}

int _tmain(int argc, _TCHAR* argv[])
{
  int cases;
    cout<<"请输入需要排序的案例个数："<<endl;
    cin>>cases;
    while(cases--)
    {
        memset(a,0.0,sizeof(a));
        int n;
        cout<<"请输入需要排序的元素的个数："<<endl;
        cin>>n;
        cout<<"请输入需要排序的元素："<<endl;
        int i = 0;
        for(i=0;i<n;i++)
        {
              cin>>a[i];
        }
        cout<<"排序前："<<endl;
        for(i=0;i<n;i++)
       {
              cout<<a[i]<<" ";
       }
       cout<<endl;
       random_fast_sort(a,0,n-1);
       cout<<"排序后："<<endl;
       for(i=0;i<n;i++)
       {
              cout<<a[i]<<" ";
       }
      cout<<endl;
   }
   system("pause");
 return 0;
}