[LeetCode] Ugly Number

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.

Credits:

Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.

解题思路：

题意为只有2、3、5三个因子的数成为Ugly Number。1也认为是Ugly Number。因此我们只需要不断的除以2/3/5即可（倘若能够整除）

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

return num==1;
}
};