LeetCode_ Factorization_ Simple_ 263. Ugly number

1. subject

Ugly numbers are just prime factors 2、3 and 5 The positive integer .

Give you an integer n , Please judge n Whether it's ugly or not . If it is , return true ; otherwise , return false .

Example 1：
Input ：n = 6
Output ：true
explain ：6 = 2 × 3

Example 2：
Input ：n = 1
Output ：true
explain ：1 No prime factor , So all its prime factors are {2, 3, 5} Empty set of . It is customary to regard it as the first ugly number .

Example 3：
Input ：n = 14
Output ：false
explain ：14 It's not ugly , Because it contains another prime factor 7 .

Tips ：
-2³¹ <= n <= 2³¹ - 1

source ： Power button （LeetCode）
link ：https://leetcode.cn/problems/ugly-number

2. Ideas

（1） Factorization
If n It's ugly , Then there must be non negative integers a、b、c, bring n == 2^a x 3^b x 5^c, And when the a = b = c = 0 when ,n = 1. So for judgment n Whether the above form is satisfied , It can be done to n Divide repeatedly by 2、3、5, until n No more prime factors 2、3、5 until . If the remaining number equals 1, shows n Excluding other prime factors , It's ugly , return true; otherwise , explain n Including other prime factors , It's not ugly , return false.

3. Code implementation （Java）

// Ideas 1———— Factorization 
class Solution {
    
    public boolean isUgly(int n) {
    
        if (n <= 0) {
    
            return false;
        }
        int[] factors = {
    2, 3, 5};
        for (int i = 0; i < factors.length; i++) {
    
            while (n % factors[i] == 0) {
    
                n /= factors[i];
            }
        }
        return n == 1;
    }
}