Leetcode: 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.

Interval as an array:

class Solution {
    public boolean canAttendMeetings(int[][] intervals) {
        if (intervals.length < 1) return true;
        
        Arrays.sort(intervals, (i1, i2) -> Integer.compare(i1[0], i2[0]));
        
        for (int i = 1; i < intervals.length; i ++) {
            if (intervals[i][0] < intervals[i - 1][1]) return false;
        }
        return true;
    }
}

Previous interval as an object:

Implement a Comparator<Interval>

Syntax: don't forget the public sign when defining a function

/**
 * 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==null || intervals.length==0 || intervals.length==1) return true;
        Comparator<Interval> comp = new Comparator<Interval>() {
            public int compare(Interval i1, Interval i2) {
                return (i1.start==i2.start)? i1.end-i2.end : i1.start-i2.start;
            }
        };
        
        Arrays.sort(intervals, comp);
        Interval pre = intervals[0];
        for (int i=1; i<intervals.length; i++) {
            Interval cur = intervals[i];
            if (cur.start < pre.end) return false;
            pre = cur;
        }
        return true;
    }
}