Write a program to find the `n`

-th ugly number.

Ugly numbers are positive numbers whose prime factors only include `2, 3, 5`

. For example, `1, 2, 3, 4, 5, 6, 8, 9, 10, 12`

is the sequence of the first `10`

ugly numbers.

Note that `1`

is typically treated as an ugly number.

class Solution(object): def min_three(self, a, b, c): minNum = min(a,b) return min(minNum,c) def nthUglyNumber(self, n): ugly = [1] factor2 = 2 factor3 = 3 factor5 = 5 index2 = index3 = index5 = 0 for i in range(1,n): minNum = min(factor2, factor3, factor5) ugly.append(minNum) if(factor2 == minNum): factor2 = 2 * ugly[index2+1] index2 += 1 if(factor3 == minNum): factor3 = 3 * ugly[index3+1] index3 += 1 if(factor5 == minNum): factor5 = 5 * ugly[index5+1] index5 += 1 return ugly[n-1]