sort函数对快排进行了优化，这里提供一个自己写的原始版本

#include <iostream>
#include <algorithm>
#include <array>
#include <vector>
#include <functional>

using namespace std;

template <class InputIterator1, class UnaryPredicate>
  void _qsort (InputIterator1 first, InputIterator1 last,UnaryPredicate pred)
{
	if(first!=last){
		auto mid=partition(first,last,bind2nd(pred,*first));//以第一号元素作为划分元素
		_qsort(first,mid,pred);
		if(first!=mid)_qsort(mid,last,pred);
		else _qsort(mid+1,last,pred);
	}
}
int main(){
	
	array<int,8> t1 = {3,5,7,11,13,17,19,23};
	array<int,8> t2 = {19,23,3,5,7,11,13,17};
										
	_qsort(t2.begin(),t2.end(),less<int>());
	
	for_each(t2.begin(),t2.end(),[](int i){cout<<i<<endl;});
	return 0;
}

C++ sort