263. Ugly Number

题目：

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.

答案：

基础因数里面只含有2或3或5的正数叫丑陋数，1是特殊的丑陋数。思路是对这三个数循环取余再判断。

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