cycle_finding.py

import unittest


def cycle_finding(n):
    m, p = 1, 1  # m.. カメの計算のあまり  p.. ウサギの計算の余り
    s, t = 0, 0  # s.. 循環節の先頭小数桁位置  t.. 循環節の末尾小数桁位置

    while True:
        m = (m * 10) % n
        p = (p * 10) % n
        p = (p * 10) % n
        if m == p:
            break

    if p != 0:
        # 循環節の先頭の検知
        p = 1
        s = 1
        while m != p:
            s += 1
            m = (m * 10) % n
            p = (p * 10) % n
        # 循環節の末尾の検知
        p = (p * 10) % n
        t = s
        while m != p:
            t += 1
            p = (p * 10) % n

    if s == 0 and t == 0:
        return 0
    else:
        return t - s + 1


class TestCycleFinding(unittest.TestCase):
    def test_1st_decimal_place(self):
        # n = 3     1 / 3 = 0.33333... -> 0.(3)
        self.assertEqual(cycle_finding(3), 1)

    def test_2nd_decimal_place(self):
        # n = 6     1 / 6 = 0.16666... -> 0.1(6)
        self.assertEqual(cycle_finding(6), 1)

    def test_max_digits(self):
        # n = 7     1 / 7 = 0.14285714285714... -> 0.(142857)
        self.assertEqual(cycle_finding(7), 6)

    def test_two_digit_number(self):
        # n = 56    1 / 56 = 0.01785714285714285... -> 0.017(857142)
        self.assertEqual(cycle_finding(56), 6)


if __name__ == '__main__':
    unittest.main()