263. 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.

Example 1:

Input: 6
Output: true
Explanation: 6 = 2 × 3

Example 2:

Input: 8
Output: true
Explanation: 8 = 2 × 2 × 2

Example 3:

Input: 14
Output: false 
Explanation: 14 is not ugly since it includes another prime factor 7.

Note:

  1. 1 is typically treated as an ugly number.
  2. Input is within the 32-bit signed integer range: [−231,  231 − 1].

Rust Solution

struct Solution;

impl Solution {
    fn is_ugly(mut num: i32) -> bool {
        if num < 1 {
            return false;
        }
        while num % 2 == 0 {
            num /= 2;
        }
        while num % 3 == 0 {
            num /= 3;
        }
        while num % 5 == 0 {
            num /= 5;
        }
        num == 1
    }
}

#[test]
fn test() {
    assert_eq!(Solution::is_ugly(6), true);
    assert_eq!(Solution::is_ugly(8), true);
    assert_eq!(Solution::is_ugly(14), false);
}

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