def merge_intervals(intervals):
    if not intervals:
        return []
    
    sorted_intervals = sorted(intervals, key=lambda x: x[0])
    merged = []
    
    current_start, current_end = sorted_intervals[0]
    
    for start, end in sorted_intervals[1:]:
        if start <= current_end:
            if end > current_end:
                current_end = end
        else:
            merged.append([current_start, current_end])
            current_start, current_end = start, end
            
    merged.append([current_start, current_end])
    return merged