Ugly Number

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

An ugly number is a positive integer whose prime factors are limited to 2, 3, and 5.

Given an integer n, return true if n is an ugly number.

Example 1:

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

Example 2:

Input: n = 1
Output: true
Explanation: 1 has no prime factors, therefore all of its prime factors are limited to 2, 3, and 5.

Example 3:

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

Solution:

The main idea here is to remember math rules and combine them in correct if-else cases. The solution is pretty forward, and I hope the code explanation is clear enough.

  public boolean isUgly(int n) {
    if (n == 0){
      return false;
    }
     
    while(n != 1){
      if (n % 2 == 0){
        n /= 2;  
      } else if (n % 3 == 0){
        n /= 3;
      } else if (n % 5 == 0){
        n /= 5;
      } else {
        return false;
      }
    }
    return true;
     
  }