21: Added path function to TreeNode (#22)

Path refers to the sequence of nodes along the edges of a tree.

build.gradle.kts

@@ -135,7 +135,11 @@ kotlin {
                 implementation(kotlin("test"))
             }
         }
-        val jvmMain by getting
+        val jvmMain by getting {
+            dependencies {
+                implementation(kotlin("script-runtime"))
+            }
+        }
         val jvmTest by getting
         val jsMain by getting
         val jsTest by getting

src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/TreeNode.kt

@@ -1,11 +1,17 @@
 package com.github.adriankuta.datastructure.tree
 
-import com.github.adriankuta.datastructure.tree.TreeNodeIterators.*
+import com.github.adriankuta.datastructure.tree.exceptions.TreeNodeException
+import com.github.adriankuta.datastructure.tree.iterators.LevelOrderTreeIterator
+import com.github.adriankuta.datastructure.tree.iterators.PostOrderTreeIterator
+import com.github.adriankuta.datastructure.tree.iterators.PreOrderTreeIterator
+import com.github.adriankuta.datastructure.tree.iterators.TreeNodeIterators
+import com.github.adriankuta.datastructure.tree.iterators.TreeNodeIterators.*
 import kotlin.jvm.JvmSynthetic
 
 open class TreeNode<T>(val value: T) : Iterable<TreeNode<T>>, ChildDeclarationInterface<T> {
 
     private var _parent: TreeNode<T>? = null
+
     /**
      * The converse notion of a child, an immediate ancestor.
      */
@@ -13,12 +19,20 @@ open class TreeNode<T>(val value: T) : Iterable<TreeNode<T>>, ChildDeclarationIn
         get() = _parent
 
     private val _children = mutableListOf<TreeNode<T>>()
+
     /**
      * A group of nodes with the same parent.
      */
     val children: List<TreeNode<T>>
         get() = _children
 
+    /**
+     * Checks whether the current tree node is the root of the tree
+     * @return `true` if the current tree node is root of the tree, `false` otherwise.
+     */
+    val isRoot: Boolean
+        get() = _parent == null
+
     /**
      * Choose one of available iterators from [TreeNodeIterators]
      */
@@ -37,7 +51,8 @@ open class TreeNode<T>(val value: T) : Iterable<TreeNode<T>>, ChildDeclarationIn
     @JvmSynthetic
     override fun child(value: T, childDeclaration: ChildDeclaration<T>?): TreeNode<T> {
         val newChild = TreeNode(value)
-        if(childDeclaration != null)
+        newChild._parent = this
+        if (childDeclaration != null)
             newChild.childDeclaration()
         _children.add(newChild)
         return newChild
@@ -91,6 +106,31 @@ open class TreeNode<T>(val value: T) : Iterable<TreeNode<T>>, ChildDeclarationIn
         return depth
     }
 
+    /**
+     * Returns the collection of nodes, which connect the current node
+     * with its descendants
+     *
+     * @param descendant the bottom child node for which the path is calculated
+     * @return collection of nodes, which connect the current node with its descendants
+     * @throws TreeNodeException exception that may be thrown in case if the
+     *                           current node does not have such descendant or if the
+     *                           specified tree node is root
+     */
+    @Throws(TreeNodeException::class)
+    fun path(descendant: TreeNode<T>): List<TreeNode<T>> {
+
+        val path = mutableListOf<TreeNode<T>>()
+        var node = descendant
+        path.add(node)
+        while (!node.isRoot) {
+            node = node.parent!!
+            path.add(node)
+            if (node == this)
+                return path
+        }
+        throw TreeNodeException("The specified tree node $descendant is not the descendant of tree node $this")
+    }
+
     /**
      * Remove all children from root and every node in tree.
      */

src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/TreeNodeExt.kt

@@ -1,5 +1,6 @@
 package com.github.adriankuta.datastructure.tree
 
+import com.github.adriankuta.datastructure.tree.iterators.TreeNodeIterators
 import kotlin.jvm.JvmSynthetic
 
 typealias ChildDeclaration<T> = ChildDeclarationInterface<T>.() -> Unit

src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/exceptions/TreeNodeException.kt

@@ -0,0 +1,6 @@
+package com.github.adriankuta.datastructure.tree.exceptions
+
+import kotlin.jvm.JvmOverloads
+
+class TreeNodeException @JvmOverloads constructor(message: String? = null, cause: Throwable? = null) :
+    RuntimeException(message, cause)

src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/iterators/LevelOrderTreeIterator.kt

@@ -1,4 +1,6 @@
-package com.github.adriankuta.datastructure.tree
+package com.github.adriankuta.datastructure.tree.iterators
+
+import com.github.adriankuta.datastructure.tree.TreeNode
 
 /**
  * Tree is iterated by using `Level-order Traversal Algorithm"

src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/iterators/PostOrderTreeIterator.kt

@@ -1,4 +1,6 @@
-package com.github.adriankuta.datastructure.tree
+package com.github.adriankuta.datastructure.tree.iterators
+
+import com.github.adriankuta.datastructure.tree.TreeNode
 
 /**
  * Tree is iterated by using `Post-order Traversal Algorithm"

src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/iterators/PreOrderTreeIterator.kt

@@ -1,4 +1,6 @@
-package com.github.adriankuta.datastructure.tree
+package com.github.adriankuta.datastructure.tree.iterators
+
+import com.github.adriankuta.datastructure.tree.TreeNode
 
 /**
  * Tree is iterated by using `Pre-order Traversal Algorithm"

src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/iterators/TreeNodeIterators.kt

@@ -1,4 +1,4 @@
-package com.github.adriankuta.datastructure.tree
+package com.github.adriankuta.datastructure.tree.iterators
 
 /**
  * @see PreOrder

src/commonTest/kotlin/com.github.adriankuta/datastructure.tree/TreeNodeTest.kt

@@ -1,5 +1,6 @@
 package com.github.adriankuta.datastructure.tree
 
+import com.github.adriankuta.datastructure.tree.iterators.TreeNodeIterators
 import kotlin.test.Test
 import kotlin.test.assertContentEquals
 import kotlin.test.assertEquals

src/jvmMain/kotlin/Example.ws.kts

@@ -0,0 +1,14 @@
+import com.github.adriankuta.datastructure.tree.tree
+
+val root =
+    tree("World") {
+        child("North America") {
+            child("USA")
+        }
+        child("Europe") {
+            child("Poland")
+            child("Germany")
+        }
+    }
+
+print(root.prettyString())