252. Meeting Rooms (1)

Link

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.

Example 1:

Input: [[0,30],[5,10],[15,20]]
Output: false

Example 2:

Input: [[7,10],[2,4]]
Output: true

NOTE: input types have been changed on April 15, 2019. Please reset to default code definition to get new method signature.

Solution

TimeComplexity: O(nlogn), by sort

class Solution {
    public boolean canAttend(int[][] intervals) {
        
        //need to sort before checking, otherwise will misjudge the ovelap case
        //ex: {[1,4][0,0]} -> misjude the [0,0] is overlapped with [1,4]
        Arrays.sort(intervals, (i1, i2) -> Integer.compare(i1[0], i2[0]));
        
        if(intervals.length <= 1){
            return true;
        }
        
        int preStart = intervals[0][0];
        int preEnd = intervals[0][1];
        
        for(int i = 1; i < intervals.length; i++){
            int curStart = intervals[i][0];
            int curEnd = intervals[i][1];
            //has overlap
            if(curStart < preEnd ){
                return false
            }
        }
        return true;
    }
}