diff --git a/maths/series/alternate_harmonic_series.py b/maths/series/alternate_harmonic_series.py new file mode 100644 index 000000000000..a887707d16fc --- /dev/null +++ b/maths/series/alternate_harmonic_series.py @@ -0,0 +1,54 @@ +def is_alternate_harmonic_series(series: list) -> bool: + """ + checking whether the input series is alternate harmonic series or not + >>> is_alternate_harmonic_series([1, -1/2, 1/3, -1/4, 1/5]) + True + >>> is_alternate_harmonic_series([2/5, -2/10, 2/15, -2/20, 2/25]) + True + >>> is_alternate_harmonic_series([1, 1/2, 1/3, 1/4]) + False + >>> is_alternate_harmonic_series([1, -1/2, 1/4, -1/8]) + False + >>> is_alternate_harmonic_series(4) + Traceback (most recent call last): + ... + ValueError: Input series is not valid, valid series - [1, 2/3, 2] + >>> is_alternate_harmonic_series([]) + Traceback (most recent call last): + ... + ValueError: Input list must be a non empty list + >>> is_alternate_harmonic_series([0]) + Traceback (most recent call last): + ... + ValueError: Input series cannot have 0 as an element + >>> is_alternate_harmonic_series([1,2,0,6]) + Traceback (most recent call last): + ... + ValueError: Input series cannot have 0 as an element + """ + if not isinstance(series, list): + raise ValueError("Input series is not valid, valid series - [1, 2/3, 2]") + if len(series) == 0: + raise ValueError("Input list must be a non empty list") + if len(series) == 1 and series[0] != 0: + return True + receprocal = [] + series_len = len(series) + for i in range(series_len): + if series[i] == 0: + raise ValueError("Input series cannot have 0 as an element") + receprocal.append(1 / series[i]) + common_diff = abs(receprocal[1]) - abs(receprocal[0]) + for index in range(2, series_len): + if ( + abs(receprocal[index]) - abs(receprocal[index - 1]) != common_diff + or receprocal[index] * receprocal[index - 1] >= 0 + ): + return False + return True + + +if __name__ == "__main__": + import doctest + + doctest.testmod()