263. Ugly Number

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.

解题思路

这道题可以不停地除2，3，5这三个因子，如果除到最后num == 1，那么这个数就是ugly number。
注意：负数不是丑陋数，要加判断

Java-Solution:

public class Solution {    public boolean isUgly(int num) {        if(num <= 0)    return false;        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 ? true : false;    }}