Leetcode Everyday: 252. Meeting Rooms

https://leetcode.com/problems/meeting-rooms/

Given an array of meeting time intervals consisting of start and end times [[s1,e1],[s2,e2],...] (si < ei), determine if a person could attend all meetings.

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

/**
 * Definition for an interval.
 * public class Interval {
 *     int start;
 *     int end;
 *     Interval() { start = 0; end = 0; }
 *     Interval(int s, int e) { start = s; end = e; }
 * }
 */
public class Solution {
    public boolean canAttendMeetings(Interval[] intervals) {
        if(intervals.length<2) return true;
        Arrays.sort(intervals, new Comparator<Interval>(){
            public int compare(Interval i1, Interval i2) {
				return i1.start-i2.start;
			}
        });
        
        for(int i=0; i<intervals.length-1;i++){
            if(intervals[i].end>intervals[i+1].start) return false;
        }
        return true;
    }
}

First sort than compare.

Another way to handle this problem is to sort the start and the end separately,  after the sorting,there are two rules:

1. it should also be correspond to each other, 

2.and the end should be less than the next start, 

if true return true, else return false. 

Because for whichever starts first mush end first, and end before another start. And for each interval because its end should be bigger than the start, we can skip the judgement of rule 1, because if they are not correspond, it will must violate the rule 2, because one of the start has a larger index of its end.