Problem

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.

Note:

1 is typically treated as an ugly number.

Input is within the 32-bit signed integer range: [−231,  231 − 1].

Pre analysis

Will factorise with 2 then 3 then 5, and find whether the divident is ugly.

Another solution

1. Iterative approach for same

   var isUgly = function(num) {
       if (num <= 0) return false;
   
       while (num > 1){
           if (num % 5 === 0){
               num /= 5;
           } else if (num % 3 === 0){
               num /= 3;
           } else if (num % 2 === 0){
               num /= 2;
           } else {
               return false;
           }
       }
   
       return true;
   };
   

---

var isUgly = function(num) {
    let primes = [2,3,5];
    let ugly = !!num;
    while(ugly) {
        ugly = primes.some(prime=>{
            if ( !(num % prime) ){
                num /= prime;
                return true;
            };
            return false;
        });
    };
    return num === 1;
};

---

var isUgly = function(num) {
    for (const p of [2, 3, 5])
    while (num && num % p == 0)
        num /= p;
    return num == 1;
};