feat: add swift implementation to lcof problem: No.32 (#2902)

Author: klever34

lcof/面试题32 - I. 从上到下打印二叉树/README.md

@@ -346,6 +346,47 @@ public class Solution {
 }
 ```
 
+#### Swift
+
+```swift
+/* public class TreeNode {
+*     var val: Int
+*     var left: TreeNode?
+*     var right: TreeNode?
+*     init(_ val: Int) {
+*         self.val = val
+*         self.left = nil
+*         self.right = nil
+*     }
+* }
+*/
+
+class Solution {
+    func levelOrder(_ root: TreeNode?) -> [Int] {
+        guard let root = root else {
+            return []
+        }
+
+        var queue: [TreeNode] = [root]
+        var result: [Int] = []
+
+        while !queue.isEmpty {
+            let node = queue.removeFirst()
+            result.append(node.val)
+
+            if let left = node.left {
+                queue.append(left)
+            }
+            if let right = node.right {
+                queue.append(right)
+            }
+        }
+
+        return result
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof/面试题32 - I. 从上到下打印二叉树/Solution.swift

@@ -0,0 +1,36 @@
+/* public class TreeNode {
+*     var val: Int
+*     var left: TreeNode?
+*     var right: TreeNode?
+*     init(_ val: Int) {
+*         self.val = val
+*         self.left = nil
+*         self.right = nil
+*     }
+* }
+*/
+
+class Solution {
+    func levelOrder(_ root: TreeNode?) -> [Int] {
+        guard let root = root else {
+            return []
+        }
+        
+        var queue: [TreeNode] = [root]
+        var result: [Int] = []
+        
+        while !queue.isEmpty {
+            let node = queue.removeFirst()
+            result.append(node.val)
+            
+            if let left = node.left {
+                queue.append(left)
+            }
+            if let right = node.right {
+                queue.append(right)
+            }
+        }
+        
+        return result
+    }
+}