263. 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.

本质上丑数就是一堆2，3，5乘在一起，其实和IsPowerof3有点类似，那个就是一堆的3成在一起。所以就是一直除2，如果能除尽就除掉，不能除尽的时候就看能否除尽3，接着到5，如果是丑数最后肯定是结果为1.

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