def merge_intervals(intervals):
    if not intervals:
        return []

    sorted_intervals = sorted((start, end) for start, end in intervals)
    merged = []

    for start, end in sorted_intervals:
        if not merged or start > merged[-1][1]:
            merged.append([start, end])
        else:
            merged[-1][1] = max(merged[-1][1], end)

    return merged