题目

A perfect power is a classification of positive integers:

In mathematics, a perfect power is a positive integer that can be expressed as an integer power of another positive integer. More formally, n is a perfect power if there exist natural numbers m > 1, and k > 1 such that m^k = n.

Your task is to check wheter a given integer is a perfect power. If it is a perfect power, return a pair m and k with m^k = n as a proof. Otherwise return Nothing, Nil, null, NULL, None or your language's equivalent.

Note: For a perfect power, there might be several pairs. For example 81 = 3^4 = 9^2, so (3,4) and (9,2) are valid solutions. However, the tests take care of this, so if a number is a perfect power, return any pair that proves it.

Examples

isPP(4) => [2,2]
isPP(9) => [3,2]
isPP(5) => None

我的答案

import math
def isPP(n):
    for m in range(2, int(math.sqrt(n))+1):
        k = int(round(math.log(n, m)))
        if m ** k == n:
            return [m, k]
    return None

• 慎用pow(a, b)函数进行开方运算，python3实测因为1/3（或1.0/3） = 0.3333333333333333，所以pow(216, 1/3) 和pow(216, 1.0/3)运行结果均为5.999999999999999，pow(216, 1/3) .is_integer()返回False。