c++ list sort

  1.    bool operator < (S & b) {
       return ID < b.ID;
      }

struct S {
         std::string firstname;
         std::string secondname;
         int ID;
      bool operator < (S & b) {
       return ID < b.ID;
      }
 // 重新定义小于，因为默认的sort函数调用的操作符是<，所以我们只需要重载 < 就好了
};

int main(int argc, char* argv[])
{

 std::list<S> mylist;

 std::list<S>::iterator iter;

 S a;

 a.firstname ="dfadf";

 a.ID = ;

 mylist.push_back (a);

 a.firstname ="得到";

 a.ID = ;

 mylist.push_back (a);

 a.firstname ="xxx";

 a.ID = ;

 mylist.push_back (a);

 a.firstname ="gggg";

 a.ID = ;

 mylist.push_back (a);

 mylist.sort();

2.

#include "stdafx.h"
#include <iostream>
#include <list>
using namespace std;

class A{
public:
    A(int m):a(m){}
    bool operator <(const A& other)
    {
    <span style="font-size: 18px;">    return a < other.a;</span>
    }
    friend std::ostream& operator <<(std::ostream& out, const A& obj){
        out<< obj.a<<endl;
        return out;
    }
private:
    int a;
};

int _tmain(int argc, _TCHAR* argv[])
{
   list<A> S;
   typedef list<A>::iterator it;
   S.push_back(A());
   S.push_back(A());
   S.push_back(A());
   S.sort();
    it it1 = S.begin();
    it it2 = S.end();
    while(it1 != it2)
    {
        cout<<*it1<<endl;
        it1++;
    }
    return ;
}

3.

 // list_sort.cpp
 // compile with: /EHsc
 #include <list>
 #include <iostream>

 int main( )
 {
    using namespace std;
    list <int> c1;
    list <int>::iterator c1_Iter;

    c1.push_back(  );
    c1.push_back(  );
    c1.push_back(  );

    cout << "Before sorting: c1 =";
    for ( c1_Iter = c1.begin( ); c1_Iter != c1.end( ); c1_Iter++ )
       cout << " " << *c1_Iter;
    cout << endl;

    c1.sort( );
    cout << "After sorting c1 =";
    for ( c1_Iter = c1.begin( ); c1_Iter != c1.end( ); c1_Iter++ )
       cout << " " << *c1_Iter;
    cout << endl;

    c1.sort( greater<int>( ) );
    cout << "After sorting with 'greater than' operation, c1 =";
    for ( c1_Iter = c1.begin( ); c1_Iter != c1.end( ); c1_Iter++ )
       cout << " " << *c1_Iter;
    cout << endl;
 }