PU 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.

C Solution:

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

Summary:

1. straightforward.
2. Be careful about num == 0.
3. 6ms, 0.7%

LeetCode: 263. Ugly Number