feat: add swift implementation to lcci problem: No.08.09 (doocs#2695)

Author: klever34

lcci/08.09.Bracket/README.md

@@ -190,6 +190,31 @@ var generateParenthesis = function (n) {
 };
 ```
 
+```swift
+class Solution {
+    private var ans: [String] = []
+    private var n: Int = 0
+
+    func generateParenthesis(_ n: Int) -> [String] {
+        self.n = n
+        dfs(l: 0, r: 0, t: "")
+        return ans
+    }
+
+    private func dfs(l: Int, r: Int, t: String) {
+        if l > n || r > n || l < r {
+            return
+        }
+        if l == n && r == n {
+            ans.append(t)
+            return
+        }
+        dfs(l: l + 1, r: r, t: t + "(")
+        dfs(l: l, r: r + 1, t: t + ")")
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- end -->

lcci/08.09.Bracket/README_EN.md

@@ -197,6 +197,31 @@ var generateParenthesis = function (n) {
 };
 ```
 
+```swift
+class Solution {
+    private var ans: [String] = []
+    private var n: Int = 0
+
+    func generateParenthesis(_ n: Int) -> [String] {
+        self.n = n
+        dfs(l: 0, r: 0, t: "")
+        return ans
+    }
+
+    private func dfs(l: Int, r: Int, t: String) {
+        if l > n || r > n || l < r {
+            return
+        }
+        if l == n && r == n {
+            ans.append(t)
+            return
+        }
+        dfs(l: l + 1, r: r, t: t + "(")
+        dfs(l: l, r: r + 1, t: t + ")")
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- end -->

lcci/08.09.Bracket/Solution.swift

@@ -0,0 +1,22 @@
+class Solution {
+    private var ans: [String] = []
+    private var n: Int = 0
+
+    func generateParenthesis(_ n: Int) -> [String] {
+        self.n = n
+        dfs(l: 0, r: 0, t: "")
+        return ans
+    }
+
+    private func dfs(l: Int, r: Int, t: String) {
+        if l > n || r > n || l < r {
+            return
+        }
+        if l == n && r == n {
+            ans.append(t)
+            return
+        }
+        dfs(l: l + 1, r: r, t: t + "(")
+        dfs(l: l, r: r + 1, t: t + ")")
+    }
+}