Project Euler 26

• 問題

Problem 26：Reciprocal cycles
A unit fraction contains 1 in the numerator. The decimal representation of the unit fractions with denominators 2 to 10 are given:
1/2 = 0.5
1/3 = 0.(3)
1/4 = 0.25
1/5 = 0.2
1/6 = 0.1(6)
1/7 = 0.(142857)
1/8 = 0.125
1/9 = 0.(1)
1/10 = 0.1
Where 0.1(6) means 0.166666..., and has a 1-digit recurring cycle. It can be seen that 1/7 has a 6-digit recurring cycle.
Find the value of d < 1000 for which 1/d contains the longest recurring cycle in its decimal fraction part.

• 解答例

maxLen = 0
index = 0

for i in range(2, 1000):
    l = 0
    r = 1
    rList = []
    while True:
        r = (r * 10) % i
        l += 1
        if r == 0 or r in rList:
            break
        rList.append(r)
    if maxLen < l:
        maxLen = l
        index = i

print(index)