find and insert after

scala/src/main/scala/ch06_linkedlist/SinglyLinkedList.scala

@@ -10,11 +10,19 @@ class SinglyLinkedList(var headOpt: Option[Node]) {
 
 
   def findByValue(value: Int): Option[Node] = {
-    None
+    headOpt.flatMap(head => {
+      var node = head
+      while (!node.data.equals(value) && node.next.nonEmpty) {
+        node = node.next.get
       }
 
-  def findByIndex(index: Int): Option[Node] = {
-    None
+      if (node.data.equals(value)) {
+        return Some(node)
+      } else {
+        //arrive the end of the chain
+        return None
+      }
+    })
   }
 
   def insertToHead(value: Int): Unit = {
@@ -55,9 +63,22 @@ class SinglyLinkedList(var headOpt: Option[Node]) {
     }
   }
 
-  def insertAfter(existNode: Node, value: Int) = {}
+  def insertAfter(existNode: Node, value: Int): Unit = {
+    val newNode = new Node(value, None)
+    insertAfter(existNode, newNode)
+  }
 
-  def insertAfter(existNode: Node, newNode: Node) = {}
+  def insertAfter(existNode: Node, newNode: Node): Unit = {
+    existNode.next match {
+      case None =>
+        //exist node is tail
+        newNode.next = None
+        existNode.next = Some(newNode)
+      case Some(next) =>
+        newNode.next = Some(next)
+        existNode.next = Some(newNode)
+    }
+  }
 
   def insertBefore(existNode: Node, value: Int) = {}
 

scala/src/test/scala/ch06_linkedlist/SinglyLinkedListTest.scala

@@ -30,4 +30,31 @@ class SinglyLinkedListTest extends FlatSpec with Matchers{
 
   }
 
+  it should "find by value" in {
+    val list: SinglyLinkedList = new SinglyLinkedList()
+
+    list.insertTail(0)
+    list.insertTail(1)
+    list.insertTail(2)
+    list.insertTail(3)
+
+    list.mkString() should equal("0123")
+    val node1 = list.findByValue(1).get
+    node1.next.get.data should equal(2)
+  }
+
+  it should "insert after node and can find it back" in {
+    val list: SinglyLinkedList = new SinglyLinkedList()
+
+    list.insertTail(0)
+    list.insertTail(1)
+    list.insertTail(3)
+    list.insertTail(4)
+
+    val node1 = list.findByValue(1).get
+    list.insertAfter(node1,2)
+
+    list.mkString() should equal("01234")
+  }
+
 }