feat: add swift implementation to lcof problem: No.53 (#2938)

Author: klever34

lcof/面试题53 - I. 在排序数组中查找数字 I/README.md

@@ -193,6 +193,35 @@ public class Solution {
 }
 ```
 
+#### Swift
+
+```swift
+class Solution {
+    private var nums: [Int] = []
+
+    func search(_ nums: [Int], _ target: Int) -> Int {
+        self.nums = nums
+        let leftIndex = search(target)
+        let rightIndex = search(target + 1)
+        return rightIndex - leftIndex
+    }
+
+    private func search(_ x: Int) -> Int {
+        var left = 0
+        var right = nums.count
+        while left < right {
+            let mid = (left + right) / 2
+            if nums[mid] >= x {
+                right = mid
+            } else {
+                left = mid + 1
+            }
+        }
+        return left
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof/面试题53 - I. 在排序数组中查找数字 I/Solution.swift

@@ -0,0 +1,24 @@
+class Solution {
+    private var nums: [Int] = []
+    
+    func search(_ nums: [Int], _ target: Int) -> Int {
+        self.nums = nums
+        let leftIndex = search(target)
+        let rightIndex = search(target + 1)
+        return rightIndex - leftIndex
+    }
+    
+    private func search(_ x: Int) -> Int {
+        var left = 0
+        var right = nums.count
+        while left < right {
+            let mid = (left + right) / 2
+            if nums[mid] >= x {
+                right = mid
+            } else {
+                left = mid + 1
+            }
+        }
+        return left
+    }
+}