feat: add swift implementation to lcof2 problem: No.070 (doocs#3222)

Author: klever34

lcof2/剑指 Offer II 070. 排序数组中只出现一次的数字/README.md

@@ -151,6 +151,28 @@ function singleNonDuplicate(nums: number[]): number {
 }
 ```
 
+#### Swift
+
+```swift
+class Solution {
+    func singleNonDuplicate(_ nums: [Int]) -> Int {
+        var left = 0
+        var right = nums.count - 1
+        
+        while left < right {
+            let mid = (left + right) / 2
+            if nums[mid] != nums[mid ^ 1] {
+                right = mid
+            } else {
+                left = mid + 1
+            }
+        }
+        
+        return nums[left]
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof2/剑指 Offer II 070. 排序数组中只出现一次的数字/Solution.swift

@@ -0,0 +1,17 @@
+class Solution {
+    func singleNonDuplicate(_ nums: [Int]) -> Int {
+        var left = 0
+        var right = nums.count - 1
+        
+        while left < right {
+            let mid = (left + right) / 2
+            if nums[mid] != nums[mid ^ 1] {
+                right = mid
+            } else {
+                left = mid + 1
+            }
+        }
+        
+        return nums[left]
+    }
+}