max of all subarrays of size k

class Solution
{
  public:
  deque<pair<int,int> > dq;
  int cnt_added=0,cnt_removed=0;
  void add(int ele){
      while(!dq.empty() and dq.back().first<ele) dq.pop_back();
      dq.push_back({ele,cnt_added});
      cnt_added++;
  }
  void del(){
      if(!dq.empty() and dq.front().second==cnt_removed) dq.pop_front();
      cnt_removed++;
  }
  int mx(){
      return dq.front().first;
  }
    //Function to find maximum of each subarray of size k.
    vector <int> max_of_subarrays(int *arr, int n, int k)
    {
        // your code here
        for(int i=0;i<k;i++) add(arr[i]);
        vector<int>ans;
        ans.push_back(mx());

        for(int i=k;i<n;i++){
            del();
            add(arr[i]);
            ans.push_back(mx());
        }
        return ans;
    }
};