嵇爾的吐槽

#没事画轮子的嵇尔不定期的(W)碎(E)碎(B)念(B)和(L)吐(O)槽(G)

Problem 35 Circular primes 2016-10-16 20:58:42

The number, 197, is called a circular prime because all rotations of the digits: 197, 971, and 719, are themselves prime.

There are thirteen such primes below 100: 2, 3, 5, 7, 11, 13, 17, 31, 37, 71, 73, 79, and 97.

How many circular primes are there below one million?


圆周素数

197被称为圆周素数,因为将它逐位旋转所得到的数:197/971和719都是素数。

小于100的圆周素数有十三个:2、3、5、7、11、13、17、31、37、71、73、79和97。

小于一百万的圆周素数有多少个?

import math

def is_Prime(number):
    if number < 2:
        return False
    for x in range(2, int(math.sqrt(number)) + 1):
        if number % x == 0:
            return False
    return True

def get_brothers(number):
    result = []
    number_level = len(str(number))
    for i in range(0, number_level):
        result.append(number)
        number_str = str(number)
        number = eval(number_str[1:] + number_str[0])
    return result

count = 0
for i in range(2, 1000001):
    if is_Prime(i) and not '0' in str(i):
        ok = True
        numbers = get_brothers(i)
        for n in numbers:
            if not is_Prime(n):
                ok = False
                break
        if ok:
            count += 1
            print i
print "count = %s" % count

感想:

  1. 一开始审题审错了,居然对着197各种排列组合……
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