[Leetcode] Ugly Number, Solution

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.

[Thoughts]

这题简单。既然已经说了ugly number是{2,3,5}的组合乘积构成的，那么判断逻辑也就简单了，对于任意一个给定的数字，拼命除这三个因子，最后能整除的就是ugly number，否则就不是。

逻辑看code

[Code]

1:  class Solution {  
2:  public:  
3:    bool isUgly(int num) {  
4:      if (num <= 0) return false;  
5:      while (num % 2 == 0) num /= 2;  
6:      while (num % 3 == 0) num /= 3;  
7:      while (num % 5 == 0) num /= 5;  
8:      return num == 1;  
9:    }  
10:  };