九层妖塔

#include <vector>
using namespace std;
class tree {
  public:
    void  (int dragon, int damage) {
      vector<int> in; 
      in.push_back (30);
      for (int i = 1; i < dragon + 1; i++) {
        in.push_back (2);
      }   
      build_tree_1 (in, damage, 1.0);
    }   
    bool result_match (vector<int> &in) {
      int cnt = 0;
      for (int i = 1; i < in.size (); i++)
        if (in[i] != 0)
          cnt++;
      return cnt == alive;
    }   
    void build_tree_1 (vector<int> &in, int damage, float p) {
      int count = 0;
      float new_p = 0.0;
#ifdef DEBUG
      for (int i = 0; i < in.size (); i++)
        cout << in[i] << ",";
      cout << "Prob " << p << " else damage " << damage << endl;
#endif
      if (damage == 0) {
        if (result_match (in))
          result += p;
        return;
      }   
      for (int i = 0; i < in.size (); i++) {
        if (in[i] != 0)
          count++;
      }
      if (count == 0)
        return;
      new_p = p / count;
      count = 0;
      for (int i = 0; i < in.size (); i++) {
        
        if (in[i] == 0)
          continue;
        in[i]--;
        build_tree_1 (in, damage - 1, new_p);
        in[i]++;
      }
    }
    tree (int dragon, int damage, int _alive) : alive (_alive) {
      result = 0.0;
      build_tree (dragon, damage);
    }
    float get_result () {
      return result;
    }
    ~tree () {
    }
  private:
    int alive;
    float result;
};
int main ()
{
  tree t (3, 8, 1);
  cout << t.get_result () << endl;
  return 0;
}