class Solution {
    public int[][] merge(int[][] intervals) {
        int n = intervals.length;
        List<int[]> res = new ArrayList<>();

        Arrays.sort(intervals, (a, b) -> Integer.compare(a[0], b[0]));
        
        int start = intervals[0][0];
        int end = intervals[0][1];

        for(int i = 1; i < n; i++) {
            if(end >= intervals[i][0]) {
                end = Math.max(end, intervals[i][1]);
            } else {
                res.add(new int[]{start, end});
                start = intervals[i][0];
                end = intervals[i][1];
            }
        }
        res.add(new int[]{start, end});

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