Python/maths/sum_of_digits.py

from timeit import timeit


def sum_of_digits(n: int) -> int:
    """
    Find the sum of digits of a number.

    >>> sum_of_digits(12345)
    15
    >>> sum_of_digits(123)
    6
    >>> sum_of_digits(-123)
    6
    >>> sum_of_digits(0)
    0
    """
    n = -n if n < 0 else n
    res = 0
    while n > 0:
        res += n % 10
        n = n // 10
    return res


def sum_of_digits_recursion(n: int) -> int:
    """
    Find the sum of digits of a number using recursion

    >>> sum_of_digits_recursion(12345)
    15
    >>> sum_of_digits_recursion(123)
    6
    >>> sum_of_digits_recursion(-123)
    6
    >>> sum_of_digits_recursion(0)
    0
    """
    n = -n if n < 0 else n
    return n if n < 10 else n % 10 + sum_of_digits(n // 10)


def sum_of_digits_compact(n: int) -> int:
    """
    Find the sum of digits of a number

    >>> sum_of_digits_compact(12345)
    15
    >>> sum_of_digits_compact(123)
    6
    >>> sum_of_digits_compact(-123)
    6
    >>> sum_of_digits_compact(0)
    0
    """
    return sum(int(c) for c in str(abs(n)))


def benchmark() -> None:
    """
    Benchmark code for comparing 3 functions,
    with 3 different length int values.
    """
    print("\nFor small_num = ", small_num, ":")
    print(
        "> sum_of_digits()",
        "\t\tans =",
        sum_of_digits(small_num),
        "\ttime =",
        timeit("z.sum_of_digits(z.small_num)", setup="import __main__ as z"),
        "seconds",
    )
    print(
        "> sum_of_digits_recursion()",
        "\tans =",
        sum_of_digits_recursion(small_num),
        "\ttime =",
        timeit("z.sum_of_digits_recursion(z.small_num)", setup="import __main__ as z"),
        "seconds",
    )
    print(
        "> sum_of_digits_compact()",
        "\tans =",
        sum_of_digits_compact(small_num),
        "\ttime =",
        timeit("z.sum_of_digits_compact(z.small_num)", setup="import __main__ as z"),
        "seconds",
    )

    print("\nFor medium_num = ", medium_num, ":")
    print(
        "> sum_of_digits()",
        "\t\tans =",
        sum_of_digits(medium_num),
        "\ttime =",
        timeit("z.sum_of_digits(z.medium_num)", setup="import __main__ as z"),
        "seconds",
    )
    print(
        "> sum_of_digits_recursion()",
        "\tans =",
        sum_of_digits_recursion(medium_num),
        "\ttime =",
        timeit("z.sum_of_digits_recursion(z.medium_num)", setup="import __main__ as z"),
        "seconds",
    )
    print(
        "> sum_of_digits_compact()",
        "\tans =",
        sum_of_digits_compact(medium_num),
        "\ttime =",
        timeit("z.sum_of_digits_compact(z.medium_num)", setup="import __main__ as z"),
        "seconds",
    )

    print("\nFor large_num = ", large_num, ":")
    print(
        "> sum_of_digits()",
        "\t\tans =",
        sum_of_digits(large_num),
        "\ttime =",
        timeit("z.sum_of_digits(z.large_num)", setup="import __main__ as z"),
        "seconds",
    )
    print(
        "> sum_of_digits_recursion()",
        "\tans =",
        sum_of_digits_recursion(large_num),
        "\ttime =",
        timeit("z.sum_of_digits_recursion(z.large_num)", setup="import __main__ as z"),
        "seconds",
    )
    print(
        "> sum_of_digits_compact()",
        "\tans =",
        sum_of_digits_compact(large_num),
        "\ttime =",
        timeit("z.sum_of_digits_compact(z.large_num)", setup="import __main__ as z"),
        "seconds",
    )


if __name__ == "__main__":
    small_num = 262144
    medium_num = 1125899906842624
    large_num = 1267650600228229401496703205376
    benchmark()
    import doctest

    doctest.testmod()