[Swift]LeetCode1012. 至少有 1 位重複的數字 | Numbers With 1 Repeated Digit

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Given a positive integer N, return the number of positive integers less than or equal to N that have at least 1 repeated digit.

Example 1:

Input: 20
Output: 1 Explanation: The only positive number (<= 20) with at least 1 repeated digit is 11. 

Example 2:

Input: 100
Output: 10 Explanation: The positive numbers (<= 100) with atleast 1 repeated digit are 11, 22, 33, 44, 55, 66, 77, 88, 99, and 100. 

Example 3:

Input: 1000
Output: 262 

Note:

1. 1 <= N <= 10^9

---

給定正整數 N，返回小於等於 N 且具備至少 1 位重複數字的正整數。 

示例 1：

輸入：20
輸出：1
解釋：具備至少 1 位重複數字的正數（<= 20）只有 11 。

示例 2：

輸入：100
輸出：10
解釋：具備至少 1 位重複數字的正數（<= 100）有 11，22，33，44，55，66，77，88，99 和 100 。

示例 3：

輸入：1000
輸出：262 

提示：

1. 1 <= N <= 10^9

---

Runtime: 4 ms

Memory Usage: 19.1 MB

 1 class Solution {
 2     func numDupDigitsAtMostN(_ N: Int) -> Int {
 3         var L:[Int] = [Int]()
 4         var x:Int = N + 1
 5         while(x > 0)
 6         {
 7             L.insert(x % 10,at:0)           
 8             x /= 10
 9         }
10         var res:Int = 0
11         var n:Int = L.count
12         for i in 1..<n
13         {
14             res += 9 * A(9, i - 1)
15         }
16         var seen:Set<Int> = Set<Int>()
17         for i in 0..<n
18         {
19             var j:Int = i > 0 ? 0 : 1
20             while(j < L[i])
21             {
22                 if !seen.contains(j)
23                 {
24                     res += A(9 - i, n - i - 1)
25                 }
26                 j += 1
27             }
28             if seen.contains(L[i]) {break}
29             seen.insert(L[i])
30         }        
31         return N - res
32     }
33     
34     func A(_ m:Int,_ n:Int) -> Int
35     {
36         return n == 0 ? 1 : A(m, n - 1) * (m - n + 1)
37     }
38 }