diff --git a/lcci/17.04.Missing Number/README.md b/lcci/17.04.Missing Number/README.md
index 77ec170e6d1aa..88ab47978b1a5 100644
--- a/lcci/17.04.Missing Number/README.md	
+++ b/lcci/17.04.Missing Number/README.md	
@@ -119,6 +119,20 @@ var missingNumber = function (nums) {
 };
 ```
 
+```swift
+class Solution {
+    func missingNumber(_ nums: [Int]) -> Int {
+        let nums = nums.sorted()
+        for (i, x) in nums.enumerated() {
+            if i != x {
+                return i
+            }
+        }
+        return nums.count
+    }
+}
+```
+
 <!-- tabs:end -->
 
 ### 方法二：求和
@@ -206,6 +220,15 @@ var missingNumber = function (nums) {
 };
 ```
 
+```swift
+class Solution {
+    func missingNumber(_ nums: [Int]) -> Int {
+        let n = nums.count
+        return n * (n + 1) / 2 - nums.reduce(0, +)
+    }
+}
+```
+
 <!-- tabs:end -->
 
 ### 方法三：位运算
diff --git a/lcci/17.04.Missing Number/README_EN.md b/lcci/17.04.Missing Number/README_EN.md
index 8d0c402b9388e..f0e867e6a31d8 100644
--- a/lcci/17.04.Missing Number/README_EN.md	
+++ b/lcci/17.04.Missing Number/README_EN.md	
@@ -119,6 +119,20 @@ var missingNumber = function (nums) {
 };
 ```
 
+```swift
+class Solution {
+    func missingNumber(_ nums: [Int]) -> Int {
+        let nums = nums.sorted()
+        for (i, x) in nums.enumerated() {
+            if i != x {
+                return i
+            }
+        }
+        return nums.count
+    }
+}
+```
+
 <!-- tabs:end -->
 
 ### Solution 2
@@ -202,6 +216,15 @@ var missingNumber = function (nums) {
 };
 ```
 
+```swift
+class Solution {
+    func missingNumber(_ nums: [Int]) -> Int {
+        let n = nums.count
+        return n * (n + 1) / 2 - nums.reduce(0, +)
+    }
+}
+```
+
 <!-- tabs:end -->
 
 ### Solution 3
diff --git a/lcci/17.04.Missing Number/Solution.swift b/lcci/17.04.Missing Number/Solution.swift
new file mode 100644
index 0000000000000..46cae2cc9e1f6
--- /dev/null
+++ b/lcci/17.04.Missing Number/Solution.swift	
@@ -0,0 +1,11 @@
+class Solution {
+    func missingNumber(_ nums: [Int]) -> Int {
+        let nums = nums.sorted()
+        for (i, x) in nums.enumerated() {
+            if i != x {
+                return i
+            }
+        }
+        return nums.count
+    }
+}
diff --git a/lcci/17.04.Missing Number/Solution2.swift b/lcci/17.04.Missing Number/Solution2.swift
new file mode 100644
index 0000000000000..ec64d3a4b404a
--- /dev/null
+++ b/lcci/17.04.Missing Number/Solution2.swift	
@@ -0,0 +1,6 @@
+class Solution {
+    func missingNumber(_ nums: [Int]) -> Int {
+        let n = nums.count
+        return n * (n + 1) / 2 - nums.reduce(0, +)
+    }
+}