Ugly Number

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.

Analyse: Continuously divide the number by 2, 3, 5. If the remaining number is one, then it's a ugly number. 

Runtime: 4ms.

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

Runtime: 8ms.

class Solution {
public:
    bool isUgly(int num) {
        if(num == 0) return false;
        if(num == 1) return true;
        
        int arr[] = {2, 3, 5};
        int index = 0;
        while(index < 3){
            while(num % arr[index] == 0) num /= arr[index];
            index++;
        }
        
        if(num == 1) return true;
        return false;
    }
};