14.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.

分析：一个数字如果只能被2,3,5整除，则为丑数。

n=2^a+3^b+5^c;

public boolean isUgly(int num) {
        if(num==1){
            return true;
        }
         
        while(num>=2 && num%2==0){
            num = num/2;
        }
        while(num>=3 && num%3==0){
            num = num/3;
        }
        while(num>=5 && num%5==0){
            num = num/5;
        }
        
        return (num==1);
    }