LeetCode - 263. 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.

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思路分析：只包括质因数2，3，5的正整数是丑数。如果一个数能连续被2整除，或连续被3整除，或连续被5整除，最后的数为1 即为丑数。

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 ) ? true : false;
    }
};