263. Ugly Number (Easy)

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.

Solution: 3ms

class Solution {
public:
    bool isUgly(int num) {
        for (int i = 2; i < 6 && num >= 2; ++i) {
            while (num % i == 0) num /= i;
        }
        return num == 1;
    }
};

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