Ugly Number I

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.

Think

• Make sure the value can be divided exactly by the divisor in array 2, 3, 5;
• So iterate the division while the value can be divided exactly, otherwise change another divisor from array.

Solution

public class Solution {
    public boolean isUgly(int num) {
        if(num<=0)
            return false;
        int[] factors = {2,3,5};
        for(int i = factors.length - 1; i >= 0; i--) {
            while(num % factors[i] == 0) {
                num /= factors[i];
            }
        }
        return num == 1;
    }
}