• Question
• Solution

Question

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

Result: Accepted Time: 4 ms

Here should be some explanations.

bool isUgly(int num) {
    if(num <= 0)
        return false;
    while(num && num % 3 == 0)
        num /= 3;
    while(num && num % 5 == 0)
        num /= 5;
    while(num && num % 2 == 0)
        num /= 2;
    return num == 1;
}

Complexity Analytics

• Time Complexity: $O(log(n))$
• Space Complexity: $O(1)$