@staticmethod
    def radix_sort(a):
        """
        -------------------------------------------------------
        Performs a base 10 radix sort.
        Use: Sorts.radix_sort(a)
        -------------------------------------------------------
        Preconditions:
            a - an array of base 10 integers (list)
        Postconditions:
            Contents of a are sorted.
        -------------------------------------------------------
        """
        RADIX = 10
        maxLength = False
        tmp , placement = -1, 1

        while not maxLength:
            maxLength = True
            # declare and initialize buckets
            buckets = [list() for _ in range(RADIX)]
            # split a between lists
            for  i in a:
                tmp = int(i / placement)
                buckets[tmp % RADIX].append(i)
                if maxLength and tmp > 0:
                    maxLength = False

            x = 0
            for b in range(RADIX):
                bucket = buckets[b]
                for i in bucket:
                    a[x] = i
                    x += 1
            # move to next digit
            placement *= RADIX
        return