BBST Using Map

#include <set>
#include <map>
#include <iostream>
#include <cstdlib>
#include <string>

using namespace std;

template<typename T>
struct Myset{
   private:
   map<T, int> mp;

   typedef _Rb_tree_node<pair<const T, int> > _Node;

   void fix_size(_Rb_tree_node_base * it, bool step_in = true){
      int & it_size = static_cast<_Node *>(it) -> _M_value_field.second;
      it_size = 1;
      if(it -> _M_left != 0){
         if(step_in)fix_size(it -> _M_left, false);
         it_size += static_cast<_Node *>(it -> _M_left) -> _M_value_field.second;
      }
      if(it -> _M_right != 0){
         if(step_in)fix_size(it -> _M_right, false);
         it_size += static_cast<_Node *>(it -> _M_right) -> _M_value_field.second;
      }
   }

   void fix_all_sizes(_Rb_tree_node_base * it, _Rb_tree_node_base * end){
      if(it -> _M_left != 0)fix_size(it -> _M_left);
      if(it -> _M_right != 0)fix_size(it -> _M_right);
      do{
         fix_size(it);
         it = it -> _M_parent;
      }while(it != end);
   }

   public:
   void print()const{
      const _Rb_tree_node_base * it = mp.begin()._M_node;
      while(it -> _M_parent != mp.end()._M_node){
         it = it -> _M_parent;
      }
      print_impl(it, "");
   }
   void print_impl(const _Rb_tree_node_base * it, string indent)const{
      if(it == 0){
         cout << indent << "nil (0)" << endl;
         return;
      }
      cout << indent << static_cast<const _Node *>(it) -> _M_value_field.first;
      cout   << " (" << static_cast<const _Node *>(it) -> _M_value_field.second << ")" << endl;
      if(it -> _M_left != 0 || it -> _M_right != 0){
         print_impl(it -> _M_left, indent + "  ");
         print_impl(it -> _M_right, indent + "  ");
      }
   }

   void insert(const T & t){
      pair<typename map<T, int>::iterator, bool> fit = mp.insert(pair<T, int>(t, -1));
      if(fit.second == false)return;
      fix_all_sizes(fit.first._M_node, mp.end()._M_node);
   }
};

int main(){
   Myset<int> st;
   for(int i = 0; i < 30; ++i)st.insert(rand() % 100);
   st.print();
}