Cinema Seat Allocation.cpp

class Solution {
public:
    int maxNumberOfFamilies(int n, vector<vector<int>>& reservedSeats) {
        unordered_map<int, vector<int>> o;
        
        for (auto r : reservedSeats) {
            
            o[r[0]].push_back(r[1]);
        }
        
        int ans = 2 * (n - o.size()); // seats with no occupancy directly adding 2
        
		// if we iterate from 1 to n (10 ^ 9) we cross time limit
        for (auto p : o) {
            
            // get reserved seats
            vector<int> seats = p.second;
            
            
            int occupied_mask = 0;
            
            // representing occupied seats as bits
            for (int s : seats) {
                if (s > 1 && s < 10) {
                    occupied_mask += (int)pow(2, 10 - s);
                }
            }
            
            // checking 3 seating configurations
            int masks[3] = {480, 120, 30};
            
            int row_ans = 0;
            bool res1 = (masks[0] & occupied_mask) == 0;
            bool res2 = (masks[1] & occupied_mask) == 0;
            bool res3 = (masks[2] & occupied_mask) == 0;
           
			// if all 3 configurations are empty, 2 families
			// if either one of them are empty, 1 family
            if (res1 && res2 && res3) row_ans += 2;
            else if (res1 || res2 || res3) row_ans += 1;
            
            
            ans += row_ans;
            
        }
        
        return ans;
    }
};