map添加元素的过程(都需要哪些操作？)

C/C++ code

#include<iostream>#include<map>using namespace std;class Car{public:  Car(int no=0){m_no=no;cout<<"creat,no is "<<no<<endl;};  Car(const Car& other){m_no=other.m_no;cout<<"copy, NO. is "<<other.m_no<<endl;};  ~Car(){;};  friend ostream& operator << (ostream& os,const Car &c);  Car& operator = (const Car& other){m_no=other.m_no;cout<<"set, NO. is "<<other.m_no<<endl;}private:  int m_no;};ostream& operator << (ostream& os,const Car &c){  os<<"The NO. of the Car is "<<c.m_no;  return os;}int main(){  map<int,Car> map_i;    Car a(1),b(2),c(3);  cout<<"start"<<endl;  map_i[1]=a;                       //创建空对象，拷贝两次后赋值  map_i.insert(pair<int,Car>(2,b)); //拷贝b三次  map_i.insert(make_pair(3,c));     //拷贝c四次  cout<<"set"<<endl;    map<int,Car>::iterator it;    for(it=map_i.begin();it!=map_i.end();it++){    cout<<it->first<<"  "<<it->second<<endl;  }}

输出：
creat,no is 1
creat,no is 2
creat,no is 3
start
creat,no is 0
copy, NO. is 0
copy, NO. is 0
set, NO. is 1
copy, NO. is 2
copy, NO. is 2
copy, NO. is 2
copy, NO. is 3
copy, NO. is 3
copy, NO. is 3
copy, NO. is 3
set
1 The NO. of the car is 1
2 The NO. of the car is 2
3 The NO. of the car is 3


每次往map里增加对象那么多拷贝，要是大对象不是很浪费时间？

为什么会有这么多拷贝呢？希望高手指点

[解决办法]

探讨

需要拷贝我知道，关键为什么那么多次？STL都干了些什么呢？