题目
Given two positive integers n and k.
A factor of an integer n is defined as an integer i where n % i == 0.
Consider a list of all factors of n sorted in ascending order, return the kth factor in this list or return -1 if n has less than k factors.
解题思路
遍历1到根号n，找出n的因子，并同时存储相乘等于n的对应的因子，如果k比前面找到的因子多，再判断是否在后面存的因子中。要处理完全平方数的情况
代码
class Solution:
def kthFactor(self, n: int, k: int) -> int:
factor = []
for i in range(1, int(math.sqrt(n)) + 1):
if n % i == 0:
k -= 1
factor.append(n // i)
if k == 0:
return i
if factor[-1] ** 2 == n:
factor.pop()
return -1 if k > len(factor) else factor[-k]
