【Python】Codility in Python : Lesson 10 - Prime and composite numbers【CountFactors】

Prime and composite numbers 第一題：【CountFactors】
Count factors of given number n.

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A positive integer D is a factor of a positive integer N
if there exists an integer M such that N = D * M.

For example, 6 is a factor of 24, because M = 4 satisfies the above condition (24 = 6 * 4).

Write a function:

　　def solution(N)

that, given a positive integer N, returns the number of its factors.

For example, given N = 24, the function should return 8,
because 24 has 8 factors, namely 1, 2, 3, 4, 6, 8, 12, 24. There are no other factors of 24.

Assume that:
　　N is an integer within the range [1..2,147,483,647].

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方法一：用平方根的方式推算
Correctness：100%、Performance：100%

import math

def solutionBySqrt(N):
  result = 0
  squareRoot = math.sqrt(N)
  for index in range(1, math.ceil(squareRoot)):
    if N % index == 0:
      result += 2

  if squareRoot == math.ceil(squareRoot):
    result += 1

  return result

方法二：用 lambda 寫法一行解決，可惜效能太差 ...
Correctness：100%、Performance：0%

def solutionByLambda(N):
  return len(list(filter(lambda x: N % x == 0, range(1, N+1))))

完整練習題 source code 請參閱：github