From cad5b2dd95b3aa57224b3365d9134eaa0713eeb9 Mon Sep 17 00:00:00 2001
From: Adrian Kuta <adrian.kuta93@gmail.com>
Date: Fri, 3 Sep 2021 13:35:18 +0200
Subject: [PATCH] Iterator class refactor

---
 treedatastructure/build.gradle                |  2 +-
 .../tree/PreOrderTreeIterator.kt              | 42 +++++++++++++++++++
 .../adriankuta/datastructure/tree/TreeNode.kt |  2 +-
 .../datastructure/tree/TreeNodeIterator.kt    | 22 ----------
 4 files changed, 44 insertions(+), 24 deletions(-)
 create mode 100644 treedatastructure/src/main/java/com/github/adriankuta/datastructure/tree/PreOrderTreeIterator.kt
 delete mode 100644 treedatastructure/src/main/java/com/github/adriankuta/datastructure/tree/TreeNodeIterator.kt

diff --git a/treedatastructure/build.gradle b/treedatastructure/build.gradle
index a2d1517..8f7ff6c 100644
--- a/treedatastructure/build.gradle
+++ b/treedatastructure/build.gradle
@@ -13,7 +13,7 @@ android {
     defaultConfig {
         minSdkVersion 15
         targetSdkVersion 31
-        versionName "2.0.2"
+        versionName "2.0.3"
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
         consumerProguardFiles 'consumer-rules.pro'
     }
diff --git a/treedatastructure/src/main/java/com/github/adriankuta/datastructure/tree/PreOrderTreeIterator.kt b/treedatastructure/src/main/java/com/github/adriankuta/datastructure/tree/PreOrderTreeIterator.kt
new file mode 100644
index 0000000..d9b3deb
--- /dev/null
+++ b/treedatastructure/src/main/java/com/github/adriankuta/datastructure/tree/PreOrderTreeIterator.kt
@@ -0,0 +1,42 @@
+package com.github.adriankuta.datastructure.tree
+
+import java.util.*
+
+/**
+ * Tree is iterated by using `Pre-order Traversal Algorithm"
+ *  1. Check if the current node is empty or null.
+ *  2. Display the data part of the root (or current node).
+ *  3. Traverse the left subtree by recursively calling the pre-order function.
+ *  4. Traverse the right subtree by recursively calling the pre-order function.
+ * ```
+ * E.g.
+ *                    1
+ *                  / | \
+ *                 /  |   \
+ *               2    3     4
+ *              / \       / | \
+ *             5    6    7  8  9
+ *            /   / | \
+ *           10  11 12 13
+ *
+ * Output: 1 2 5 10 6 11 12 13 3 4 7 8 9
+ * ```
+ */
+class PreOrderTreeIterator<T>(root: TreeNode<T>) : Iterator<TreeNode<T>> {
+
+    private val stack = Stack<TreeNode<T>>()
+
+    init {
+        stack.push(root)
+    }
+
+    override fun hasNext(): Boolean = !stack.empty()
+
+    override fun next(): TreeNode<T> {
+        val node = stack.pop()
+        node.children
+            .asReversed()
+            .forEach { stack.push(it) }
+        return node
+    }
+}
\ No newline at end of file
diff --git a/treedatastructure/src/main/java/com/github/adriankuta/datastructure/tree/TreeNode.kt b/treedatastructure/src/main/java/com/github/adriankuta/datastructure/tree/TreeNode.kt
index da49fdb..7a896f8 100644
--- a/treedatastructure/src/main/java/com/github/adriankuta/datastructure/tree/TreeNode.kt
+++ b/treedatastructure/src/main/java/com/github/adriankuta/datastructure/tree/TreeNode.kt
@@ -137,5 +137,5 @@ open class TreeNode<T>(val value: T) : Iterable<TreeNode<T>>, ChildDeclarationIn
      * Output: 1 2 5 10 6 11 12 13 3 4 7 8 9
      * ```
      */
-    override fun iterator(): Iterator<TreeNode<T>> = TreeNodeIterator(this)
+    override fun iterator(): Iterator<TreeNode<T>> = PreOrderTreeIterator(this)
 }
\ No newline at end of file
diff --git a/treedatastructure/src/main/java/com/github/adriankuta/datastructure/tree/TreeNodeIterator.kt b/treedatastructure/src/main/java/com/github/adriankuta/datastructure/tree/TreeNodeIterator.kt
deleted file mode 100644
index 115c1c2..0000000
--- a/treedatastructure/src/main/java/com/github/adriankuta/datastructure/tree/TreeNodeIterator.kt
+++ /dev/null
@@ -1,22 +0,0 @@
-package com.github.adriankuta.datastructure.tree
-
-import java.util.*
-
-class TreeNodeIterator<T>(root: TreeNode<T>) : Iterator<TreeNode<T>> {
-
-    private val stack = Stack<TreeNode<T>>()
-
-    init {
-        stack.push(root)
-    }
-
-    override fun hasNext(): Boolean = !stack.empty()
-
-    override fun next(): TreeNode<T> {
-        val node = stack.pop()
-        node.children
-            .asReversed()
-            .forEach { stack.push(it) }
-        return node
-    }
-}
\ No newline at end of file