【问题描述】存在一类特殊的数字,其因子只包含3,5,7;例如:3,5,7,9,15,21,请问第50个因子数是?
【输入形式】无
【输出形式】仅输出第50个因子数即可
【样例输入】
【样例输出】
【样例说明】
【评分标准】
def find_special_number(n):
special_numbers = [1]
p3 = p5 = p7 = 0
while len(special_numbers) < n:
next3 = special_numbers[p3] * 3
next5 = special_numbers[p5] * 5
next7 = special_numbers[p7] * 7
next_num = min(next3, next5, next7)
special_numbers.append(next_num)
if next_num == next3:
p3 += 1
if next_num == next5:
p5 += 1
if next_num == next7:
p7 += 1
return special_numbers[-1]
print(find_special_number(51))