Ugly Number

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.

Solution1: recursive

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

Solution2: iterative

public class Solution {
    public boolean isUgly(int num) {
        int div = 2 * 3 * 5;
        
        while (num > 0 && div > 1) {
            if (num % div == 0) {
                num /= div;
            }
            
            if (num % 2 != 0 && div % 2 == 0) {
                div /= 2;
            }
            
            if (num % 3 != 0 && div % 3 == 0) {
                div /= 3;
            }
            
            if (num % 5 != 0 && div % 5 == 0) {
                div /= 5;
            }
        }
        
        return num == 1;
    }
}