添加 107.二叉树的层次遍历II Scala版本

problems/0102.二叉树的层序遍历.md

@@ -553,6 +553,33 @@ func levelOrderBottom(_ root: TreeNode?) -> [[Int]] {
 }
 ```
 
+Scala:
+```scala
+// 107.二叉树的层次遍历II
+object Solution {
+  import scala.collection.mutable
+  def levelOrderBottom(root: TreeNode): List[List[Int]] = {
+    val res = mutable.ListBuffer[List[Int]]()
+    if (root == null) return res.toList
+    val queue = mutable.Queue[TreeNode]()
+    queue.enqueue(root)
+    while (!queue.isEmpty) {
+      val tmp = mutable.ListBuffer[Int]()
+      val len = queue.size
+      for (i <- 0 until len) {
+        val curNode = queue.dequeue()
+        tmp.append(curNode.value)
+        if (curNode.left != null) queue.enqueue(curNode.left)
+        if (curNode.right != null) queue.enqueue(curNode.right)
+      }
+      res.append(tmp.toList)
+    }
+    // 最后翻转一下
+    res.reverse.toList
+  }
+}
+```
+
 # 199.二叉树的右视图
 
 [力扣题目链接](https://leetcode-cn.com/problems/binary-tree-right-side-view/)