@@ -470,5 +470,56 @@ func postorder(_ root: TreeNode?, res: inout [Int]) {
470470 res.append (root! .val )
471471}
472472```
473+ Scala: 前序遍历:(144.二叉树的前序遍历)
474+ ``` scala
475+ object Solution {
476+ import scala .collection .mutable .ListBuffer
477+ def preorderTraversal (root : TreeNode ): List [Int ] = {
478+ val res = ListBuffer [Int ]()
479+ def traversal (curNode : TreeNode ): Unit = {
480+ if (curNode == null ) return
481+ res.append(curNode.value)
482+ traversal(curNode.left)
483+ traversal(curNode.right)
484+ }
485+ traversal(root)
486+ res.toList
487+ }
488+ }
489+ ```
490+ 中序遍历:(94. 二叉树的中序遍历)
491+ ``` scala
492+ object Solution {
493+ import scala .collection .mutable .ListBuffer
494+ def inorderTraversal (root : TreeNode ): List [Int ] = {
495+ val res = ListBuffer [Int ]()
496+ def traversal (curNode : TreeNode ): Unit = {
497+ if (curNode == null ) return
498+ traversal(curNode.left)
499+ res.append(curNode.value)
500+ traversal(curNode.right)
501+ }
502+ traversal(root)
503+ res.toList
504+ }
505+ }
506+ ```
507+ 后序遍历:(145. 二叉树的后序遍历)
508+ ``` scala
509+ object Solution {
510+ import scala .collection .mutable .ListBuffer
511+ def postorderTraversal (root : TreeNode ): List [Int ] = {
512+ val res = ListBuffer [Int ]()
513+ def traversal (curNode : TreeNode ): Unit = {
514+ if (curNode == null ) return
515+ traversal(curNode.left)
516+ traversal(curNode.right)
517+ res.append(curNode.value)
518+ }
519+ traversal(root)
520+ res.toList
521+ }
522+ }
523+ ```
473524-----------------------
474525<div align =" center " ><img src =https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width =500 > </img ></div >
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