263. Ugly Number

题目来源【Leetcode】

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.

用每个因子去除，看能否除尽：

class Solution {
public:
    bool isUgly(int num) {
    if(num < 1) return false;
    for (int i=2; i < 6; i++){
       while (num % i == 0)
          num = num/i;
    }
    return num == 1;
    }
};