C++(11)：emplace_back

C++11为容器增加了emplace_back成员函数，改函数可以改善push_back的效率：

#include 
#include 
using namespace std;
 
class A{
public:
	A(int i)
	{
		cout<<"A construct, this:"<<this<
	}
	A(const A &a)
	{
		cout<<"A copy construct, this:"<<this<<" ori:"<<&a<
	}
	~A()
	{
		cout<<"A deconstruct, this:"<<this<
	}
};
 
int main() {
	vector v;
	v.push_back(1);
    return 0;
}

#include &l