Look and say in C++, reimplementation of algorithm first written in Haskell

LookAndSay.cpp

/*
g++ -O3 -mtune=native -march=native -fomit-frame-pointer lookandsay.cpp -o lookandsay.out
time ./lookandsay.out > /dev/null
./lookandsay.out > /dev/null  2,88s user 0,05s system 99% cpu 2,948 total
*/



#include <vector>
#include <iostream>

using namespace std;

inline void render(int i, vector< int > & vec)
{
  vector< int >::iterator it;
  int sum = 0;
  for(it = vec.begin(); *it > 0; it++)
    {
      cout << *it;
      sum += *it;
    }
  cout << endl;
  cerr << "(" << i+1 << "," << sum << ")" << endl;
  cout << vec.size() << endl;
}

int main()
{
  vector< int > v1;
  vector< int > v2;
  vector< int >::iterator it;

  v1.push_back(1);
  v2.push_back(-1);
  v2.push_back(-1);

  int i;

  for(i = 0; i < 59; i++)
    {
      render(i, v1);

      it = v1.begin();
      v2.clear();
      
      while(*it > 0)
      {
        if (*it == *(it+1))
          {
            if (*(it+1) == *(it+2))
              {
                v2.push_back(3);
                v2.push_back(*it);
                it+=3;
              }
            else
              {
                v2.push_back(2);
                v2.push_back(*it);
                it+=2;
              }
          }
        else
          {
            v2.push_back(1);
            v2.push_back(*it);
            it+=1;
          }
      }

      v2.push_back(-1);
      v2.push_back(-1);
      v1.clear();
      v1 = v2;
      
    }
  
  render(i, v1);
  
  return 0;
}