Args:
        n (int):

    Returns:
        int: the n-th fibonacci number

    References:
        http://stackoverflow.com/questions/15047116/iterative-alg-fib

    CommandLine:
        python -m utool.util_alg fibonacci_iterative

    Example:
        >>> # ENABLE_DOCTEST
        >>> from utool.util_alg import *  # NOQA
        >>> import utool as ut
        >>> with ut.Timer('fib iter'):
        >>>     series = [fibonacci_iterative(n) for n in range(20)]
        >>> result = ('series = %s' % (str(series[0:10]),))
        >>> print(result)
        series = [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]

def fibonacci_iterative(n):
    """
    Args:
        n (int):

    Returns:
        int: the n-th fibonacci number

    References:
        http://stackoverflow.com/questions/15047116/iterative-alg-fib

    CommandLine:
        python -m utool.util_alg fibonacci_iterative

    Example:
        >>> # ENABLE_DOCTEST
        >>> from utool.util_alg import *  # NOQA
        >>> import utool as ut
        >>> with ut.Timer('fib iter'):
        >>>     series = [fibonacci_iterative(n) for n in range(20)]
        >>> result = ('series = %s' % (str(series[0:10]),))
        >>> print(result)
        series = [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]
    """
    a, b = 0, 1
    for _ in range(0, n):
        a, b = b, a + b
    return a