def find_largest_hotspot(centroid_list: list) -> int:
    """
    Description: Find the size of the cluster with the most data points

    :param centroid_list: list of centroid for each final cluster.
        each centroid in form of [longitude, latitude, # location]
    :return: an integer which is the length of the longest cluster
    """
    largest_hotspot = 0     # set the current largest size
    for a_centroid in centroid_list:    # iterate through each centroid
        if a_centroid[2] > largest_hotspot: # if [# location] > the current largest size
            largest_hotspot = a_centroid[2] # change the largest size to the size of this centroid
    return largest_hotspot