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;

}