feat: add swift implementation to lcci problem: No.08.07 (doocs#2693)

Author: klever34

lcci/08.07.Permutation I/README.md

@@ -208,6 +208,39 @@ var permutation = function (S) {
 };
 ```
 
+```swift
+class Solution {
+    private var s: [Character] = []
+    private var vis: [Bool] = Array(repeating: false, count: 128)
+    private var ans: [String] = []
+    private var t: String = ""
+
+    func permutation(_ S: String) -> [String] {
+        s = Array(S)
+        dfs(0)
+        return ans
+    }
+
+    private func dfs(_ i: Int) {
+        if i == s.count {
+            ans.append(t)
+            return
+        }
+        for c in s {
+            let index = Int(c.asciiValue!)
+            if vis[index] {
+                continue
+            }
+            vis[index] = true
+            t.append(c)
+            dfs(i + 1)
+            t.removeLast()
+            vis[index] = false
+        }
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- end -->

lcci/08.07.Permutation I/README_EN.md

@@ -213,6 +213,39 @@ var permutation = function (S) {
 };
 ```
 
+```swift
+class Solution {
+    private var s: [Character] = []
+    private var vis: [Bool] = Array(repeating: false, count: 128)
+    private var ans: [String] = []
+    private var t: String = ""
+
+    func permutation(_ S: String) -> [String] {
+        s = Array(S)
+        dfs(0)
+        return ans
+    }
+
+    private func dfs(_ i: Int) {
+        if i == s.count {
+            ans.append(t)
+            return
+        }
+        for c in s {
+            let index = Int(c.asciiValue!)
+            if vis[index] {
+                continue
+            }
+            vis[index] = true
+            t.append(c)
+            dfs(i + 1)
+            t.removeLast()
+            vis[index] = false
+        }
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- end -->

lcci/08.07.Permutation I/Solution.swift

@@ -0,0 +1,30 @@
+class Solution {
+    private var s: [Character] = []
+    private var vis: [Bool] = Array(repeating: false, count: 128)
+    private var ans: [String] = []
+    private var t: String = ""
+
+    func permutation(_ S: String) -> [String] {
+        s = Array(S)
+        dfs(0)
+        return ans
+    }
+
+    private func dfs(_ i: Int) {
+        if i == s.count {
+            ans.append(t)
+            return
+        }
+        for c in s {
+            let index = Int(c.asciiValue!)
+            if vis[index] {
+                continue
+            }
+            vis[index] = true
+            t.append(c)
+            dfs(i + 1)
+            t.removeLast()
+            vis[index] = false
+        }
+    }
+}