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#include<iostream>
#include<vector>
#include<stack>
#include<cstdlib>
#include<algorithm>
using
namespace std;
/**把数组分为两部分，轴pivot左边的部分都小于轴右边的部分**/
template
<typename
Comparable>
int
partition(vector<Comparable> &vec,int
low,int
high){
Comparable pivot=vec[low];
//任选元素作为轴，这里选首元素
while(low<high){
while(low<high && vec[high]>=pivot)
high--;
vec[low]=vec[high];
while(low<high && vec[low]<=pivot)
low++;
vec[high]=vec[low];
}
//此时low==high
vec[low]=pivot;
return
low;
}
/**使用递归快速排序**/
template<typename
Comparable>
void
quicksort1(vector<Comparable> &vec,int
low,int
high){
if(low<high){
int
mid=partition(vec,low,high);
quicksort1(vec,low,mid-1);
quicksort1(vec,mid+1,high);
}
}
/**使用栈的非递归快速排序**/
template<typename
Comparable>
void
quicksort2(vector<Comparable> &vec,int
low,int
high){
stack<int> st;
if(low<high){
int
mid=partition(vec,low,high);
if(low<mid-1){
st.push(low);
st.push(mid-1);
}
if(mid+1<high){
st.push(mid+1);
st.push(high);
}
//其实就是用栈保存每一个待排序子串的首尾元素下标，下一次while循环时取出这个范围，对这段子序列进行partition操作
while(!st.empty()){
int
q=st.top();
st.pop();
int
p=st.top();
st.pop();
mid=partition(vec,p,q);
if(p<mid-1){
st.push(p);
st.push(mid-1);
}
if(mid+1<q){
st.push(mid+1);
st.push(q);
}
}
}
}
int
main(){
int
len=1000000;
vector<int> vec;
for(int
i=0;i<len;i++)
vec.push_back(rand());
clock_t
t1=clock();
quicksort1(vec,0,len-1);
clock_t
t2=clock();
cout<<"recurcive "<<1.0*(t2-t1)/CLOCKS_PER_SEC<<endl;
//重新打乱顺序
random_shuffle(vec.begin(),vec.end());
t1=clock();
quicksort2(vec,0,len-1);
t2=clock();
cout<<"none recurcive "<<1.0*(t2-t1)/CLOCKS_PER_SEC<<endl;
return
0;
}
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