feat: add swift implementation to lcof2 problem: No.006 (doocs#2976)

* Swift implementation for LCOF2 006

* Update README.md

* Update Solution.swift

---------

Co-authored-by: Libin YANG <contact@yanglibin.info>

Author: klever34

lcof2/剑指 Offer II 006. 排序数组中两个数字之和/README.md

@@ -191,6 +191,33 @@ impl Solution {
 }
 ```
 
+#### Swift
+
+```swift
+class Solution {
+    func twoSum(_ numbers: [Int], _ target: Int) -> [Int] {
+        let n = numbers.count
+        for i in 0..<n {
+            let x = target - numbers[i]
+            var l = i + 1
+            var r = n - 1
+            while l < r {
+                let mid = (l + r) / 2
+                if numbers[mid] >= x {
+                    r = mid
+                } else {
+                    l = mid + 1
+                }
+            }
+            if l < n && numbers[l] == x {
+                return [i, l]
+            }
+        }
+        return []
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof2/剑指 Offer II 006. 排序数组中两个数字之和/Solution.swift

@@ -0,0 +1,22 @@
+class Solution {
+    func twoSum(_ numbers: [Int], _ target: Int) -> [Int] {
+        let n = numbers.count
+        for i in 0..<n {
+            let x = target - numbers[i]
+            var l = i + 1
+            var r = n - 1
+            while l < r {
+                let mid = (l + r) / 2
+                if numbers[mid] >= x {
+                    r = mid
+                } else {
+                    l = mid + 1
+                }
+            }
+            if l < n && numbers[l] == x {
+                return [i, l]
+            }
+        }
+        return []
+    }
+}