【LeetCode】253.Meeting Rooms II(Medium)解题报告

【LeetCode】253.Meeting Rooms II(Medium)解题报告

题目地址：https://leetcode.com/problems/meeting-rooms-ii/（带锁题）

题目描述：

  Given an array of meeting time intervals consisting of start and end times [[s1,e1],[s2,e2],…] (si < ei), find the minimum number of conference rooms required.

  For example, Given [[0, 30],[5, 10],[15, 20]], return 2.

  非常重要，面试经常出现。

Solution1:

time:O(nlogn)
space:O(n)
public int minMeetingRooms(Intervals[] intervals){
int[] starts = new int[intervals.length];
int[] ends = new int[intervals.length];
for(int i=0 ; i<intervals.length ; i++){
starts[i] = intervals[i].start;
ends[i] = intervals[i].end;
}
Arrays.sort(starts);
Arrays.sort(ends);
int res = 0;
int end = 0;
for(int i=0 ; i<intervals.length ; i++){
if(starts[i]<ends[end]){
res++;
}else end++;
}
return res;
}

Solution2：

time:O(nlogn)
space:O(n)
public int minMeetingRooms(Intervals[] intervals){
Arrays.sort(intervals,(a,b)->a.start-b.start);
PriorityQuene<Interval> heap = new PriorityQuene<>(intervals.length,(a,b)->a.end-b.end);
heap.offer(intervals[0]);
for(int i=1 ; i<intervals.length ; i++){
Interval interval = heap.poll();
if(intervals[i].start >= interval.end){
interval.end = intervals[i].end;
}else{
heap.offer(intervals[i]);
}
heap.offer(interval);
}
return heap.size();
}

Date：2018年2月19日