Function solution

project_euler/problem_002/sol4.py:22–69

Returns the sum of all even fibonacci sequence elements that are lower or equal to n. >>> solution(10) 10 >>> solution(15) 10 >>> solution(2) 2 >>> solution(1) 0 >>> solution(34) 44 >>> solution(3.4) 2 >>> solution(0) Traceback (most

(n: int = 4000000)

def solution(n: int = 4000000) -> int:
    """
    Returns the sum of all even fibonacci sequence elements that are lower
    or equal to n.

    >>> solution(10)
    10
    >>> solution(15)
    10
    >>> solution(2)
    2
    >>> solution(1)
    0
    >>> solution(34)
    44
    >>> solution(3.4)
    2
    >>> solution(0)
    Traceback (most recent call last):
        ...
    ValueError: Parameter n must be greater than or equal to one.
    >>> solution(-17)
    Traceback (most recent call last):
        ...
    ValueError: Parameter n must be greater than or equal to one.
    >>> solution([])
    Traceback (most recent call last):
        ...
    TypeError: Parameter n must be int or castable to int.
    >>> solution("asd")
    Traceback (most recent call last):
        ...
    TypeError: Parameter n must be int or castable to int.
    """

    try:
        n = int(n)
    except TypeError, ValueError:
        raise TypeError("Parameter n must be int or castable to int.")
    if n <= 0:
        raise ValueError("Parameter n must be greater than or equal to one.")
    getcontext().prec = 100
    phi = (Decimal(5) ** Decimal("0.5") + 1) / Decimal(2)

    index = (math.floor(math.log(n * (phi + 2), phi) - 1) // 3) * 3 + 2
    num = Decimal(round(phi ** Decimal(index + 1))) / (phi + 2)
    total = num // 2
    return int(total)


if __name__ == "__main__":