Ugly Number

Problem Description

Write a program to check whether a given number is an ugly number.

Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. For example, 6, 8 are ugly while 14 is not ugly since it includes another prime factor 7.

Note that 1 is typically treated as an ugly number.

Solution
We continuously divide the number we need to check by 2, 3, and 5, until that number is not divisible by 2, 3 or 5. If the final result is not equal to 1, the original number is not a ugly number. Otherwise, it is. This is a warm-up exercise for this problem.

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;
    }
}