添加 199.二叉树的右视图 Scala版本

problems/0102.二叉树的层序遍历.md

@@ -750,6 +750,31 @@ func rightSideView(_ root: TreeNode?) -> [Int] {
 }
 ```
 
+Scala:
+```scala
+// 199.二叉树的右视图
+object Solution {
+  import scala.collection.mutable
+  def rightSideView(root: TreeNode): List[Int] = {
+    val res = mutable.ListBuffer[Int]()
+    if (root == null) return res.toList
+    val queue = mutable.Queue[TreeNode]()
+    queue.enqueue(root)
+    while (!queue.isEmpty) {
+      val len = queue.size
+      var curNode: TreeNode = null
+      for (i <- 0 until len) {
+        curNode = queue.dequeue()
+        if (curNode.left != null) queue.enqueue(curNode.left)
+        if (curNode.right != null) queue.enqueue(curNode.right)
+      }
+      res.append(curNode.value)   // 把最后一个节点的值加入解集
+    }
+    res.toList  // 最后需要把res转换为List，return关键字可以省略
+  }
+}
+```
+
 # 637.二叉树的层平均值
 
 [力扣题目链接](https://leetcode-cn.com/problems/average-of-levels-in-binary-tree/)