Stars energy, dp

stars.cpp

  map<vector<int>, int > dp;

  int rec(vector<int> v){
    if(dp.find(v) != dp.end()){
      return dp[v];
    }

    if(v.size() == 2){
      return 0;
    }

    int max_en = 0;

    for(int i = 1; i < v.size() - 1; i++){
      int el = v[i];
      v.erase(v.begin() + i);
      int val = v[i-1] * v[i+1] + rec(v);
      v.insert(v.begin() + i, el);

      max_en = max(val, max_en);
    }

    return max_en;
  }