partition(a[], p, r)
{
i = p
j = p-1
ref = a[r]
for(; i<r; i++)
{　　
if(a[i]<ref)
{
j++
exchange(a[i], a[j])
}
}
exchange(a[r], a[j+1])
return j+1;
}

partition(a[], p, r){
refId = random(p,r)
i = p
j = p-1
for(; i<=r; i++)
{
if(a[i]<ref)
{
j++ if(j == refId)//此时j刚好等refId，并且要和a[i]交换，则更新refId { refId = i }
exchange(a[i], a[j])
}
}
exchange(a[j+1], a[refId])
return j+1
}

#include <iostream>
#include <stack>
#include"stdlib.h"
#include <time.h>

using namespace std;
template<class T>
class SORT
{
public:
static void myQsort(T a[], int p, int r);
static void myQsortNoRecur(T a[], int p, int r);
private:
static int partition(T a[], int p, int r);
static void exchange(T a[], int i, int j);
};
template<class T>
void SORT<T>::exchange(T a[], int i, int j)
{
T temp = a[i];
a[i] = a[j];
a[j] = temp;
return;
}
template<class T>
int SORT<T>::partition(T a[],int p,int r)
{
int i = p;
int j = p-1;
T ref = a[p];
int refId = p;
srand((unsigned)time(NULL));
refId = (rand() % (r-p+1))+ p;
//cout<<refId<<endl;
ref = a[refId];
for(; i<=r; i++)
{
if(a[i] < ref)
{
j++;
exchange(a, i, j);
if(j == refId)
{
refId = i;
}
}
}
exchange(a, j+1, refId);
return j+1;
}
template<class T>
void SORT<T>::myQsort(T a[],int p,int r)
{
int q = 0;
if(p<r)
{
q = partition(a, p, r);
myQsort(a, p, q-1);
myQsort(a, p+1, r);
}
return;
}
template<class T>
void SORT<T>::myQsortNoRecur(T a[], int p, int r)
{
int start = p;
int end = r;
int mid = 0;
std::stack<int> sortStk;

sortStk.push(p);
sortStk.push(r);

while(!sortStk.empty())
{
end = sortStk.top();
sortStk.pop();
start = sortStk.top();
sortStk.pop();
if(start < end)
{
mid = partition(a, start, end);
sortStk.push(start);
sortStk.push(mid -1);
sortStk.push(mid + 1);
sortStk.push(end);
}
}
}
int main(int argc, char** argv)
{
int a[10];
int b[10];
srand((unsigned)time(NULL));
for(int i=0; i<9; i++)
{
a[i] = rand();
}

srand((unsigned)time(NULL));
for(int i=0; i<9; i++)
{
b[i] = rand();
}

SORT<int>::myQsort(a,0, 9);

SORT<int>::myQsortNoRecur(b,0, 9);

for(int i=0; i<10; i++)
{
cout<<a[i]<<" ";
}
cout<<endl;
for(int i=0; i<10; i++)
{
cout<<b[i]<<" ";
}
return 0;
}

template<class T>
void SORT<T>::myQsort(T a[],int p,int r)
{
int q = 0;
if(p<r)
{
q = partition(a, p, r);
myQsort(a, p, q-1);
myQsort(a, p+1, r);
}
return;

}

template<class T>
void SORT<T>::myQsortNoRecur(T a[], int p, int r)
{
int start = p;
int end = r;
int mid = 0;
std::stack<int> sortStk;

sortStk.push(p);
sortStk.push(r);

while(!sortStk.empty())
{
end = sortStk.top();
sortStk.pop();
start = sortStk.top();
sortStk.pop();
if(start < end)
{
mid = partition(a, start, end);
sortStk.push(start);
sortStk.push(mid -1);
sortStk.push(mid + 1);
sortStk.push(end);
}
}
}