feat: add swift implementation to lcci problem: No.17.19 (#2806)

Author: klever34

lcci/17.19.Missing Two/README.md

@@ -142,6 +142,42 @@ func missingTwo(nums []int) []int {
 }
 ```
 
+```swift
+class Solution {
+    func missingTwo(_ nums: [Int]) -> [Int] {
+        let n = nums.count + 2
+        var xor = 0
+        
+        for num in nums {
+            xor ^= num
+        }
+        
+        for i in 1...n {
+            xor ^= i
+        }
+        
+        let diff = xor & (-xor)
+        
+        var a = 0
+        
+        for num in nums {
+            if (num & diff) != 0 {
+                a ^= num
+            }
+        }
+        
+        for i in 1...n {
+            if (i & diff) != 0 {
+                a ^= i
+            }
+        }
+        
+        let b = xor ^ a
+        return [a, b]
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- end -->

lcci/17.19.Missing Two/README_EN.md

@@ -135,6 +135,42 @@ func missingTwo(nums []int) []int {
 }
 ```
 
+```swift
+class Solution {
+    func missingTwo(_ nums: [Int]) -> [Int] {
+        let n = nums.count + 2
+        var xor = 0
+        
+        for num in nums {
+            xor ^= num
+        }
+        
+        for i in 1...n {
+            xor ^= i
+        }
+        
+        let diff = xor & (-xor)
+        
+        var a = 0
+        
+        for num in nums {
+            if (num & diff) != 0 {
+                a ^= num
+            }
+        }
+        
+        for i in 1...n {
+            if (i & diff) != 0 {
+                a ^= i
+            }
+        }
+        
+        let b = xor ^ a
+        return [a, b]
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- end -->

lcci/17.19.Missing Two/Solution.swift

@@ -0,0 +1,33 @@
+class Solution {
+    func missingTwo(_ nums: [Int]) -> [Int] {
+        let n = nums.count + 2
+        var xor = 0
+        
+        for num in nums {
+            xor ^= num
+        }
+        
+        for i in 1...n {
+            xor ^= i
+        }
+        
+        let diff = xor & (-xor)
+        
+        var a = 0
+        
+        for num in nums {
+            if (num & diff) != 0 {
+                a ^= num
+            }
+        }
+        
+        for i in 1...n {
+            if (i & diff) != 0 {
+                a ^= i
+            }
+        }
+        
+        let b = xor ^ a
+        return [a, b]
+    }
+}