LeetCode—253.会議室II(Meeting Rooms II)——分析とコード(C++)

class Solution {
public:
    int minMeetingRooms(vector<vector<int>>& intervals) {
        if (intervals.empty())
            return 0;
        vector<int> begin_time(intervals.size());//          
        vector<int> end_time(intervals.size());//         
        for (int i = 0; i < intervals.size(); i++) {
            begin_time[i] = intervals[i][0];
            end_time[i] = intervals[i][1];
        }
        sort(begin_time.begin(), begin_time.end());
        sort(end_time.begin(), end_time.end());
        int room = 0, free_room = 0, endnum = 0;//     ，       ，        
        for (int i = 0; i < intervals.size(); i++) {
            int time = begin_time[i];
            while (endnum < intervals.size() && end_time[endnum] < time + 1) {//             
                endnum++;
                free_room++;
            }
            if (free_room > 0)//      ，  1      
                free_room--;
            else//      ，     
                room++;
        }
        return room;
    }
};