class Solution {
    public int[][] merge(int[][] intervals) {

        List<int[]> result = new ArrayList<>();
        Arrays.sort(intervals, Comparator.comparingInt(a -> a[0])); //nlogn

        int start = intervals[0][0], end = intervals[0][1];

        for (int i=1; i<intervals.length; i++) {
            if (intervals[i][0] <= end && intervals[i][1] > end) {
                end = intervals[i][1];
            }else if (intervals[i][0] > end) {
                result.add(new int[]{start, end});
                start = intervals[i][0];
                end = intervals[i][1];
            }
        }

        return result.toArray(new int[result.size()][]);
    }
}