253. Meeting Rooms II

/**
 * Definition for an interval.
 * struct Interval {
 *     int start;
 *     int end;
 *     Interval() : start(0), end(0) {}
 *     Interval(int s, int e) : start(s), end(e) {}
 * };
 */
class Solution {
public:
    int minMeetingRooms(vector<Interval>& intervals) {
        sort(intervals.begin(),intervals.end(),[](Interval a,Interval b){return a.start<b.start;});
        priority_queue<int,vector<int>, greater<int>> pq;
        int res=0;
        for(auto interval:intervals)
        {
            while(!pq.empty()&&interval.start>=pq.top()) pq.pop();
            pq.push(interval.end);
            int size = pq.size();
            res = max(res,size);
        }
        return res;
    }
};