252 Meeting Rooms

Given an array of meeting time intervals where intervals[i] = [starti, endi], determine if a person could attend all meetings.

Example 1:

Input: intervals = [[0,30],[5,10],[15,20]]
Output: false
Example 2:

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

public boolean canAttendMeetings(int[][] intervals) { 
        if(intervals.length==0)return true;
        Arrays.sort(intervals , (a,b)->Integer.compare(a[0],b[0])); //O(nlogn)
        Stack<int[]> stack = new Stack(); //O(n)
        stack.add(intervals[0]);
        
        for(int i=1;i<intervals.length;i++){
            
            int startpoint2 = intervals[i][0];
            int endpoint2 = intervals[i][1];
                                       
            int[] poparray = stack.pop();
            int startpoint1 = poparray[0];
            int endpoint1 = poparray[1];
            
            if(endpoint1>startpoint2){
                return false;
            }
            
            stack.add(intervals[i]);
        }
        
        return true;
    
    }