Data commit

Task/Tree-traversal/Scala/tree-traversal.scala

@@ -0,0 +1,55 @@
+case class IntNode(value: Int, left: Option[IntNode] = None, right: Option[IntNode] = None) {
+
+  def preorder(f: IntNode => Unit) {
+    f(this)
+    left.map(_.preorder(f)) // Same as: if(left.isDefined) left.get.preorder(f)
+    right.map(_.preorder(f))
+  }
+
+  def postorder(f: IntNode => Unit) {
+    left.map(_.postorder(f))
+    right.map(_.postorder(f))
+    f(this)
+  }
+
+  def inorder(f: IntNode => Unit) {
+    left.map(_.inorder(f))
+    f(this)
+    right.map(_.inorder(f))
+  }
+
+  def levelorder(f: IntNode => Unit) {
+
+    def loVisit(ls: List[IntNode]): Unit = ls match {
+      case Nil => None
+      case node :: rest => f(node); loVisit(rest ++ node.left ++ node.right)
+    }
+
+    loVisit(List(this))
+  }
+}
+
+object TreeTraversal extends App {
+  implicit def intNode2SomeIntNode(n: IntNode) = Some[IntNode](n)
+
+  val tree = IntNode(1,
+    IntNode(2,
+      IntNode(4,
+        IntNode(7)),
+      IntNode(5)),
+    IntNode(3,
+      IntNode(6,
+        IntNode(8),
+        IntNode(9))))
+
+  List(
+    "  preorder: " -> tree.preorder _, // `_` denotes the function value of type `IntNode => Unit` (returning nothing)
+    "   inorder: " -> tree.inorder _,
+    " postorder: " -> tree.postorder _,
+    "levelorder: " -> tree.levelorder _) foreach {
+      case (name, func) =>
+        val s = new StringBuilder(name)
+        func(n => s ++= n.value.toString + " ")
+        println(s)
+    }
+}