263. Ugly Number*

​​https://leetcode.com/problems/ugly-number/​​

題目描述

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​

​.

Example 1:

Input: 6
Output: true
Explanation: 6 = 2 × 3      

Example 2:

Input: 8
Output: true
Explanation: 8 = 2 × 2 × 2      

Example 3:

Input: 14
Output: false 
Explanation: 14 is not ugly since it includes another prime factor 7.      

• 1 is typically treated as an ugly number.
• Input is within the 32-bit signed integer range:.

C++ 實作 1

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;
    }
};