263. Ugly Number

1.描述

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.

2.分析

3.代码

class Solution {
public:
    bool isUgly(int num) {
        if (num <= 0) return false;
        if (num == 1 || num == 2 || num == 3 || num == 5) return true;
        
        while (num % 2 == 0) { num /= 2; }
        while (num % 3 == 0) { num /= 3; }
        while (num % 5 == 0) { num /= 5; }
        
        if (num != 1 && num != 2 && num != 3 && num != 5) return false;
        return true;        
    }
};