feat: add swift implementation to lcof problem: No.03 (#2829)

Author: klever34

lcof/面试题03. 数组中重复的数字/README.md

@@ -197,6 +197,22 @@ class Solution {
 }
 ```
 
+#### Swift
+
+```swift
+class Solution {
+    func findRepeatNumber(_ nums: [Int]) -> Int {
+        let sortedNums = nums.sorted()
+        for i in 0..<sortedNums.count - 1 {
+            if sortedNums[i] == sortedNums[i + 1] {
+                return sortedNums[i]
+            }
+        }
+        return -1
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof/面试题03. 数组中重复的数字/Solution.swift

@@ -0,0 +1,11 @@
+class Solution {
+    func findRepeatNumber(_ nums: [Int]) -> Int {
+        let sortedNums = nums.sorted()
+        for i in 0..<sortedNums.count - 1 {
+            if sortedNums[i] == sortedNums[i + 1] {
+                return sortedNums[i]
+            }
+        }
+        return -1
+    }
+}