[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.

解題思路：

題意爲只有2、3、5三個因子的數成爲Ugly Number。1也認爲是Ugly Number。因此我們只需要不斷的除以2/3/5即可（倘若能夠整除）

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;
    }
};