feat: add swift implementation to lcof2 problem: No.014 (doocs#2984)

Author: klever34

lcof2/剑指 Offer II 014. 字符串中的变位词/README.md

@@ -440,6 +440,44 @@ function checkInclusion(s1: string, s2: string): boolean {
 }
 ```
 
+#### Swift
+
+```swift
+class Solution {
+    func checkInclusion(_ s1: String, _ s2: String) -> Bool {
+        let m = s1.count
+        let n = s2.count
+        if m > n {
+            return false
+        }
+        
+        var cnt1 = [Int](repeating: 0, count: 26)
+        var cnt2 = [Int](repeating: 0, count: 26)
+        let aAscii = Character("a").asciiValue!
+        
+        for i in 0..<m {
+            cnt1[Int(s1[s1.index(s1.startIndex, offsetBy: i)].asciiValue! - aAscii)] += 1
+            cnt2[Int(s2[s2.index(s2.startIndex, offsetBy: i)].asciiValue! - aAscii)] += 1
+        }
+        
+        if cnt1 == cnt2 {
+            return true
+        }
+        
+        for i in m..<n {
+            cnt2[Int(s2[s2.index(s2.startIndex, offsetBy: i)].asciiValue! - aAscii)] += 1
+            cnt2[Int(s2[s2.index(s2.startIndex, offsetBy: i - m)].asciiValue! - aAscii)] -= 1
+            
+            if cnt1 == cnt2 {
+                return true
+            }
+        }
+        
+        return false
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof2/剑指 Offer II 014. 字符串中的变位词/Solution.swift

@@ -0,0 +1,33 @@
+class Solution {
+    func checkInclusion(_ s1: String, _ s2: String) -> Bool {
+        let m = s1.count
+        let n = s2.count
+        if m > n {
+            return false
+        }
+        
+        var cnt1 = [Int](repeating: 0, count: 26)
+        var cnt2 = [Int](repeating: 0, count: 26)
+        let aAscii = Character("a").asciiValue!
+        
+        for i in 0..<m {
+            cnt1[Int(s1[s1.index(s1.startIndex, offsetBy: i)].asciiValue! - aAscii)] += 1
+            cnt2[Int(s2[s2.index(s2.startIndex, offsetBy: i)].asciiValue! - aAscii)] += 1
+        }
+        
+        if cnt1 == cnt2 {
+            return true
+        }
+        
+        for i in m..<n {
+            cnt2[Int(s2[s2.index(s2.startIndex, offsetBy: i)].asciiValue! - aAscii)] += 1
+            cnt2[Int(s2[s2.index(s2.startIndex, offsetBy: i - m)].asciiValue! - aAscii)] -= 1
+            
+            if cnt1 == cnt2 {
+                return true
+            }
+        }
+        
+        return false
+    }
+}