517. Ugly Number

Posted 2021-02-04 lawrenceseattle

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.

Example
Given num = 8 return true
Given num = 14 return false

Notice
Note that 1 is typically treated as an ugly number.

public class Solution {
    /**
     * @param num: An integer
     * @return: true if num is an ugly number or false
     */
    // 如果能整除2 3 5 就除一次，直到最后不能除
    public boolean isUgly(int num) {
        while(num >= 2) {
            if(num % 2 == 0) num /= 2;
            else if(num % 3 == 0) num /= 3;
            else if(num % 5 == 0) num /= 5;
            else
                return false;
        }
        return num == 1;
    }
}