feat: add swift implementation to lcof2 problem: No.069 (#3221)

Author: klever34

lcof2/剑指 Offer II 069. 山峰数组的顶部/README.md

@@ -182,6 +182,26 @@ var peakIndexInMountainArray = function (arr) {
 };
 ```
 
+#### Swift
+
+```swift
+class Solution {
+    func peakIndexInMountainArray(_ arr: [Int]) -> Int {
+        var left = 1
+        var right = arr.count - 2
+        while left < right {
+            let mid = (left + right) / 2
+            if arr[mid] > arr[mid + 1] {
+                right = mid
+            } else {
+                left = mid + 1
+            }
+        }
+        return left
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof2/剑指 Offer II 069. 山峰数组的顶部/Solution.swift

@@ -0,0 +1,16 @@
+class Solution {
+    func peakIndexInMountainArray(_ arr: [Int]) -> Int {
+        var left = 1
+        var right = arr.count - 2
+        while left < right {
+            let mid = (left + right) / 2
+            if arr[mid] > arr[mid + 1] {
+                right = mid
+            } else {
+                left = mid + 1
+            }
+        }
+        return left
+    }
+}
+