def counting_sort(arr):
    if not arr:
        return arr
    maximum = max(arr)
    counts = [0] * (maximum + 1)
    for num in arr:
        counts[num] += 1
    result = []
    for value, count in enumerate(counts):
        result.extend([value] * count)
    return result

print(counting_sort([4, 2, 2, 8, 3, 3, 1]))