07/16/2016 Math

## 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: $O(1)$