def normalize(X, mu=0, std=1):
    """Normalizes the input array with mean mu and standard deviation std

    :param X: Input array to be normalized
    :type X: numpy.ndarray
    :param mu: The mean, defaults to 0
    :type mu: int, optional
    :param std: The standard deviation, defaults to 1
    :type std: int, optional
    :return: The normalized array
    :rtype: nnumpy.ndarray
    """
    return (X - mu) / std