feat: implement MCTS

[Samarium150]

Close #46

[Samarium150]

which part is the rollout of MCTS

simulate

[pwyq]

You may not use a using-directive to make all names from a namespace available.

// Forbidden -- This pollutes the namespace.
using namespace foo;

https://google.github.io/styleguide/cppguide.html#Namespaces

I am changing every using namespace solver::helper;

[Samarium150]

You may not use a using-directive to make all names from a namespace available.

// Forbidden -- This pollutes the namespace.
using namespace foo;

https://google.github.io/styleguide/cppguide.html#Namespaces

I am changing every using namespace solver::helper;

Did I use it somewhere? I totally forgot.

[pwyq]

How did you run MCTS

I am doing

      MCTS* mcts = new MCTS(game);
      res_move   = mcts->search();
      delete mcts;

I got

terminate called after throwing an instance of 'std::invalid_argument'
  what():  Cannot play at 2 2 with value 2, which is already filled. Full game = 22.*131*..2

[Samarium150]

terminate called after throwing an instance of 'std::invalid_argument'
  what():  Cannot play at 2 2 with value 2, which is already filled. Full game = 22.*131*..2

Probably something wrong with simulate

[pwyq]

PR #71 is ready. It will marge into this 46-mcts branch