void Board::traverse (Tile *t, Neighbours neighbours) {
  t->visited = true;
  COO coo = make_pair(t->i, t->j);
  Buddies buddies = neighbours[coo];
  if (t->color != '0' && t->color != '.') {
    for (uint i = 0; i < buddies.size(); i++) {
      Tile *buddy = &this->field[buddies[i]];
      if (buddy->visited && buddy->color == t->color) {
        if (buddy->chain_id == -1) {
          buddy->chain_id = this->chains.size();
          this->chains[buddy->chain_id].push_back(*buddy);
        }
        t->chain_id = buddy->chain_id;
        this->chains[t->chain_id].push_back(*t);
        break;
      }
    }
    if (t->chain_id == -1) {
      t->chain_id = this->chains.size();
      this->chains[t->chain_id].push_back(*t);
    }
  }

  for (uint i = 0; i < buddies.size(); i++) {
    if (!this->field[buddies[i]].visited) {
      this->traverse(&this->field[buddies[i]], neighbours);
    }
  }
}

class Board():

    def __init__(self, s):
        self.field = []
        self.chains = {}
        self.heights = None
        self.score = 0
        self.step = 1

    def traverse(self, t=None):
        t.visited = True
        buddies = neighbours[(t.i, t.j)]
        if t.color != '0' and t.color != '.':
            for i, j in buddies:
                if self.field[i][j].visited and self.field[i][j].color == t.color:
                    if self.field[i][j].chain_id is None:
                        self.field[i][j].chain_id = len(self.chains)
                        self.chains[self.field[i][j].chain_id] = [self.field[i][j]]
                    t.chain_id = self.field[i][j].chain_id
                    self.chains[t.chain_id].append(t)
                    break
            if t.chain_id is None:
                t.chain_id = len(self.chains)
                self.chains[t.chain_id] = [t]

        for i, j in buddies:
            if not self.field[i][j].visited:
                self.traverse(self.field[i][j])