56. Merge Intervals

// 56. Merge Intervals
//5ms 94.88% fast
//41.3MB 88.02% fast
class Solution {
    public int[][] merge(int[][] intervals) {
        List<int[]> res=new ArrayList<>();
        
        if(intervals.length==0 || intervals==null)
            return res.toArray(new int[0][]);
        
        Arrays.sort(intervals, (a,b) -> a[0]-b[0]);
        
        int start=intervals[0][0];
        int end=intervals[0][1];
        
        for(int[] i:intervals){
            if(i[0]<=end){
                end=Math.max(end,i[1]);
            }
            else{
                res.add(new int[]{start,end});
                start=i[0];
                end=i[1];
            }
        }
        res.add(new int[]{start,end});        
        return res.toArray(new int[0][]);
    }
}