LeetCode 253. Meeting Rooms II

 253. Meeting Rooms II

Given an array of meeting time intervals intervals where intervals[i] = [starti, endi], return the minimum number of conference rooms required.

 

Example 1:

Input: intervals = [[0,30],[5,10],[15,20]]
Output: 2

Example 2:

Input: intervals = [[7,10],[2,4]]
Output: 1

 

Constraints:

• 1 <= intervals.length <= 104
• 0 <= starti < endi <= 106

	class Solution {
	public:
	int minMeetingRooms(vector<vector<int>>& intervals) {
	// sort by start time
	sort(intervals.begin(), intervals.end(), [&](vector<int> x, vector<int> y){
	return x[0] < y[0];
	});
	// keep end times
	priority_queue<int, vector<int>, greater<>> min_heap;
	int n = intervals.size();
	for(int i = 0; i < n; i++){
	int start = intervals[i][0];
	int end = intervals[i][1];
	// use existing room (means have to remove)
	if(!min_heap.empty() and start >= min_heap.top()){
	min_heap.pop();
	}
	// add new room
	min_heap.push(end);
	}
	return min_heap.size();
	}
	};

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