[Swift]LeetCode263. 丑数 | Ugly Number

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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:  is not ugly since it includes another prime factor .
147

Note:

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

编写一个程序判断给定的数是否为丑数。

丑数就是只包含质因数 2, 3, 5 的正整数。

示例 1:

输入: 6
输出: true
解释: 6 = 2 × 3

示例 2:

输入: 8
输出: true
解释: 8 = 2 × 2 × 2

示例 3:

输入: 14
输出: false 
解释:  不是丑数，由于它包含了另一个质因数 。147

说明：

1. 1 是丑数。
2. 输入不会超过 32 位有符号整数的范围: [−231,  231 − 1]。

---

 

20ms

 1 class Solution {
 2     func isUgly(_ num: Int) -> Bool {
 3         if num < 1 {return false}
 4         var number:Int = num
 5         while (number % 2 == 0)
 6         {
 7             number /= 2
 8         }
 9         while (number % 3 == 0)
10         {
11             number /= 3
12         }
13         while (number % 5 == 0)
14         {
15             number /= 5
16         }
17         return number == 1
18     }
19 }

---

16ms

 1 class Solution {
 2     func maxDiv(_ num: inout Int, _ div: Int) {
 3         while (num % div == 0) {
 4             num = num/div
 5         }
 6     }
 7     
 8     func isUgly(_ num: Int) -> Bool {
 9         if(num == 0) {
10             return false
11         }
12         var no = num
13         maxDiv(&no, 2)
14         maxDiv(&no, 3)
15         maxDiv(&no, 5)
16         
17         if(no == 1){
18             return true
19         }
20         else {
21             return false
22         }
23         
24     }
25 }

---

20ms

 1 class Solution {
 2     func isUgly(_ num: Int) -> Bool {
 3         guard num > 0 else {return false}
 4         var n = num
 5         
 6         let divs = [2, 3, 5]
 7         for d in divs {
 8             while n % d == 0 {
 9                 n /= d
10             }
11         }
12         return n == 1
13     }
14 }