def merge_intervals(intervals):
    if not intervals:
        return []
    sorted_intervals = sorted(intervals, key=lambda x: x[0])
    merged = []
    for interval in sorted_intervals:
        if not merged:
            merged.append(interval[:])
        else:
            last = merged[-1]
            if last[1] >= interval[0]:
                last[1] = max(last[1], interval[1])
            else:
                merged.append(interval[:])
    return merged