添加 0226.翻转二叉树.md Scala版本

problems/0226.翻转二叉树.md

@@ -820,5 +820,53 @@ func invertTree(_ root: TreeNode?) -> TreeNode? {
 }
 ```
 
+### Scala
+
+深度优先遍历（前序遍历）:
+```scala
+object Solution {
+  def invertTree(root: TreeNode): TreeNode = {
+    if (root == null) return root
+    // 递归
+    def process(node: TreeNode): Unit = {
+      if (node == null) return
+      // 翻转节点
+      val curNode = node.left
+      node.left = node.right
+      node.right = curNode
+      process(node.left)
+      process(node.right)
+    }
+    process(root)
+    root
+  }
+}
+```
+
+广度优先遍历（层序遍历）:
+```scala
+object Solution {
+  import scala.collection.mutable
+  def invertTree(root: TreeNode): TreeNode = {
+    if (root == null) return root
+    val queue = mutable.Queue[TreeNode]()
+    queue.enqueue(root)
+    while (!queue.isEmpty) {
+      val len = queue.size
+      for (i <- 0 until len) {
+        var curNode = queue.dequeue()
+        if (curNode.left != null) queue.enqueue(curNode.left)
+        if (curNode.right != null) queue.enqueue(curNode.right)
+        // 翻转
+        var tmpNode = curNode.left
+        curNode.left = curNode.right
+        curNode.right = tmpNode
+      }
+    }
+    root
+  }
+}
+```
+
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