添加 226.翻转二叉树 Swift版本

problems/0226.翻转二叉树.md

@@ -609,5 +609,43 @@ struct TreeNode* invertTree(struct TreeNode* root){
 }
 ```
 
+### Swift：
+```swift
+// 前序遍历-递归
+func invertTree(_ root: TreeNode?) -> TreeNode? {
+    guard let root = root else {
+        return root
+    }
+    let tmp = root.left
+    root.left = root.right
+    root.right = tmp
+    let _ = invertTree(root.left)
+    let _ = invertTree(root.right)
+    return root
+}
+
+// 层序遍历-迭代
+func invertTree1(_ root: TreeNode?) -> TreeNode? {
+    guard let root = root else {
+        return nil
+    }
+    var queue = [TreeNode]()
+    queue.append(root)
+    while !queue.isEmpty {
+        let node = queue.removeFirst()
+        let tmp = node.left
+        node.left = node.right
+        node.right = tmp
+        if let left = node.left {
+            queue.append(left)
+        }
+        if let right = node.right {
+            queue.append(right)
+        }
+    }
+    return root
+}
+```
+
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 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>