leetcode_253_会议室 II

class Solution {
    	public int minMeetingRooms(int[][] intervals) {
		if (intervals == null || intervals.length == 0)
			return 0;
		PriorityQueue<Integer> heap = new PriorityQueue<Integer>();

		Arrays.sort(intervals, (o1, o2) -> o1[0] - o2[0]);
		heap.add(intervals[0][1]);
		for (int i = 1; i < intervals.length; i++) {
			if (heap.peek() <= intervals[i][0]) {
				heap.remove();
			}
			heap.add(intervals[i][1]);
		}
		return heap.size();
	}
}

class Solution {
   	public int minMeetingRooms(int[][] intervals) {
		if (intervals == null || intervals.length == 0)
			return 0;
		int[] starts = new int[intervals.length];
		int[] ends = new int[intervals.length];
		for (int i = 0; i < intervals.length; i++) {
			starts[i] = intervals[i][0];
			ends[i] = intervals[i][1];
		}
		Arrays.sort(starts);
		Arrays.sort(ends);
		int count = 0;
		int endIdx = 0;
		for (int start : starts) {
			if (start >= ends[endIdx]) {
				endIdx++;
			} else {
				count++;
			}
		}
		return count;
	}
}