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题目链接：https://leetcode.com/problems/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.

思路：
easy 时间复杂度O(n)

算法：

[java] view plain copy  

1. public boolean isUgly(int num) {  
2.     if (num <= 0) {  
3.         return false;  
4.     }  
5.     while (num % 2 == 0)  
6.         num /= 2;  
7.     while (num % 3 == 0)  
8.         num /= 3;  
9.     while (num % 5 == 0)  
10.         num /= 5;  
11.   
12.     if (num == 1) {  
13.         return true;  
14.     } else {  
15.         return false;  
16.     }  
17. }  

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