会社で少し盛り上がった Project Euler をやってみる 014 ref: https://qiita.com/junichiro/items/42b5dea47b5030097ddf

file0.txt

import sys
from multiprocessing import Pool

class Problem14:

    CASH = {}

    def main(self, n):
        result = 1
        num = 1
        for i in range(2, n):
            count = p.collatzNumCount(i)
            self.CASH[i] = count
            if result < count:
                num = i
                result = count
        print(num, result)

    def collatzNumCount(self, n):
        i = 0
        while(n != 1):
            if n in self.CASH:
                i += self.CASH[n]
                return i
            n = self.collatzNum(n)
            i += 1
        return i

    def collatzNum(self, n):
        if n % 2 == 0:
            return self._collatzEven(n)
        else:
            return self._collatzOdd(n)

    def _collatzOdd(self, n):
        return 3 * n + 1

    def _collatzEven(self, n):
        return n / 2


if __name__ == '__main__':
    num = 1000000
    if len(sys.argv) == 2:
        num = sys.argv[1]
    p = Problem14()
    p.main(int(num))