Leetcode 263. Ugly Number

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

Which means an ugly number is 2^i * 3^j * 5^k * 1 (i,j,k are non-negative integers).

Therefore, we can keep dividing the given number with 2, 3, 5 until its not dividable by 2,3,5.

Then we can determine it is an ugly number if the remaining is equal to 1.

public class Solution { public boolean isUgly(int num) { if (num <= 0) return false; while (num%2==0) num /= 2; while (num%3==0) num /= 3; while (num%5==0) num /= 5; return num == 1; } }