请列举几个不同的 n 值(如 n=  120, 7, 27)，分别求出 hailstone 的返回值，体会证明算法有穷性的困难。

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# @Time : 2020/5/27 15:51
# @Author : caius
# @Site : 
# @File : day4.py
# @Software: PyCharm

import numpy as np
import matplotlib.pyplot as plt

def hailstone(n):
    length = 1
    while(1<n):
        if n %2 == 0:
            n = n//2
        else:
            n = n*3+1
        length += 1
    return length


if __name__ == '__main__':
    x = [n for n in range(10000)]
    y = [hailstone(h) for h in x]

    plt.scatter(x,y)
    plt.xticks(np.arange(min(x),max(x)+1,1000))
    plt.xlabel('n')
    plt.ylabel('hailstone(n)')
    plt.show()