Add tree traversal

Author: Romanow

README.md

@@ -58,9 +58,14 @@
 ## Algorithms
 
 1. Bubble Sort – [solution](src/main/kotlin/ru/romanow/algorithms/BubbleSort.kt), [test](src/test/kotlin/ru/romanow/algorithms/BubbleSortTest.kt)
-2. Selection Sort – [solution](src/main/kotlin/ru/romanow/algorithms/InsertionSort.kt), [test](src/test/kotlin/ru/romanow/algorithms/InsertionSortTest.kt)
+2. Insertion Sort – [solution](src/main/kotlin/ru/romanow/algorithms/InsertionSort.kt), [test](src/test/kotlin/ru/romanow/algorithms/InsertionSortTest.kt)
 3. Selection Sort – [solution](src/main/kotlin/ru/romanow/algorithms/SelectionSort.kt), [test](src/test/kotlin/ru/romanow/algorithms/SelectionSortTest.kt)
 4. Quick Sort – [solution](src/main/kotlin/ru/romanow/algorithms/QuickSort.kt), [test](src/test/kotlin/ru/romanow/algorithms/QuickSortTest.kt)
 5. Merge Sort – [solution](src/main/kotlin/ru/romanow/algorithms/MergeSort.kt), [test](src/test/kotlin/ru/romanow/algorithms/MergeSortTest.kt)
+6. Binary Search Tree – [solution](src/main/kotlin/ru/romanow/algorithms/BinarySearchTree.kt), [test](src/test/kotlin/ru/romanow/algorithms/BinarySearchTreeTest.kt)
+7. Pre-order Deep First Search Traversal – [solution](src/main/kotlin/ru/romanow/algorithms/PreOrderDeepFirstSearch.kt), [test](src/test/kotlin/ru/romanow/algorithms/PreOrderDeepFirstSearchTest.kt)
+8. In-order Deep First Search Traversal – [solution](src/main/kotlin/ru/romanow/algorithms/InOrderDeepFirstSearch.kt), [test](src/test/kotlin/ru/romanow/algorithms/InOrderDeepFirstSearchTest.kt)
+9. Post-order Deep First Search Traversal – [solution](src/main/kotlin/ru/romanow/algorithms/PostOrderDeepFirstSearch.kt), [test](src/test/kotlin/ru/romanow/algorithms/PostOrderDeepFirstSearchTest.kt)
+10. Breadth First Search Traversal – [solution](src/main/kotlin/ru/romanow/algorithms/BreadthFirstSearch.kt), [test](src/test/kotlin/ru/romanow/algorithms/BreadthFirstSearchTest.kt)
 
 [//]: # (@formatter:on)

src/main/kotlin/ru/romanow/algorithms/BreadthFirstSearch.kt

@@ -0,0 +1,24 @@
+package ru.romanow.algorithms
+
+import ru.romanow.models.TreeNode
+import java.util.LinkedList
+
+class BreadthFirstSearch {
+    fun traverse(root: TreeNode?): List<Int> {
+        val result = mutableListOf<Int>()
+        if (root == null) {
+            return result
+        }
+
+        val queue = LinkedList<TreeNode>()
+        queue.add(root)
+
+        while (queue.isNotEmpty()) {
+            val node = queue.poll()
+            result.add(node.value)
+            node.left?.let { queue.add(it) }
+            node.right?.let { queue.add(it) }
+        }
+        return result
+    }
+}

src/main/kotlin/ru/romanow/algorithms/InOrderDeepFirstSearch.kt

@@ -0,0 +1,14 @@
+package ru.romanow.algorithms
+
+import ru.romanow.models.TreeNode
+
+class InOrderDeepFirstSearch {
+    fun traverse(node: TreeNode?): List<Int> {
+        if (node == null) {
+            return emptyList()
+        }
+        return traverse(node.left) +
+            listOf(node.value) +
+            traverse(node.right)
+    }
+}

src/main/kotlin/ru/romanow/algorithms/PostOrderDeepFirstSearch.kt

@@ -0,0 +1,14 @@
+package ru.romanow.algorithms
+
+import ru.romanow.models.TreeNode
+
+class PostOrderDeepFirstSearch {
+    fun traverse(node: TreeNode?): List<Int> {
+        if (node == null) {
+            return emptyList()
+        }
+        return traverse(node.right) +
+            traverse(node.left) +
+            listOf(node.value)
+    }
+}

src/main/kotlin/ru/romanow/algorithms/PreOrderDeepFirstSearch.kt

@@ -0,0 +1,14 @@
+package ru.romanow.algorithms
+
+import ru.romanow.models.TreeNode
+
+class PreOrderDeepFirstSearch {
+    fun traverse(node: TreeNode?): List<Int> {
+        if (node == null) {
+            return emptyList()
+        }
+        return listOf(node.value) +
+            traverse(node.left) +
+            traverse(node.right)
+    }
+}

src/main/kotlin/ru/romanow/algorithms/TreeTraversal.kt

@@ -1,12 +1,21 @@
 package ru.romanow.models
 
-import java.util.*
+import java.util.LinkedList
+import kotlin.collections.ArrayList
 
 data class TreeNode(var value: Int) {
     var left: TreeNode? = null
     var right: TreeNode? = null
 }
 
+fun printTree(node: TreeNode?, level: Int = 0) {
+    if (node == null) return
+    print("  ".repeat(level))
+    println("├─ ${node.value}")
+    printTree(node.left, level + 1)
+    printTree(node.right, level + 1)
+}
+
 fun buildListFromTree(root: TreeNode?): List<Int?> {
     val list = ArrayList<Int?>()
     if (root != null) {

src/main/kotlin/ru/romanow/models/TreeNode.kt

@@ -7,6 +7,7 @@ import org.junit.jupiter.params.provider.Arguments
 import org.junit.jupiter.params.provider.ArgumentsProvider
 import org.junit.jupiter.params.provider.ArgumentsSource
 import ru.romanow.models.buildTreeFromList
+import ru.romanow.models.printTree
 import java.util.stream.Stream
 
 class BinarySearchTreeTest {
@@ -15,6 +16,8 @@ class BinarySearchTreeTest {
     @ParameterizedTest(name = "#{index} – Search {1} in tree {0}")
     fun flatten(items: List<Int?>, target: Int, result: Int?) {
         val root = buildTreeFromList(items)
+        printTree(root)
+
         val obj = BinarySearchTree()
         assertThat(obj.find(root, target)?.value).isEqualTo(result)
     }

src/test/kotlin/ru/romanow/algorithms/BinarySearchTreeTest.kt

@@ -0,0 +1,29 @@
+package ru.romanow.algorithms
+
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.extension.ExtensionContext
+import org.junit.jupiter.params.ParameterizedTest
+import org.junit.jupiter.params.provider.Arguments
+import org.junit.jupiter.params.provider.ArgumentsProvider
+import org.junit.jupiter.params.provider.ArgumentsSource
+import ru.romanow.models.buildTreeFromList
+import ru.romanow.models.printTree
+import java.util.stream.Stream
+
+class BreadthFirstSearchTest {
+
+    @ArgumentsSource(ValueProvider::class)
+    @ParameterizedTest(name = "#{index} – Bfs {0} is {1}")
+    fun flatten(items: List<Int?>, result: List<Int>) {
+        val root = buildTreeFromList(items)
+        printTree(root)
+
+        val obj = BreadthFirstSearch()
+        assertThat(obj.traverse(root)).isEqualTo(result)
+    }
+
+    internal class ValueProvider : ArgumentsProvider {
+        override fun provideArguments(context: ExtensionContext): Stream<Arguments> =
+            Stream.of(Arguments.of(listOf(10, 5, 15, 3, 7, 12, 20), listOf(10, 5, 15, 3, 7, 12, 20)))
+    }
+}

src/test/kotlin/ru/romanow/algorithms/BreadthFirstSearchTest.kt

@@ -0,0 +1,29 @@
+package ru.romanow.algorithms
+
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.extension.ExtensionContext
+import org.junit.jupiter.params.ParameterizedTest
+import org.junit.jupiter.params.provider.Arguments
+import org.junit.jupiter.params.provider.ArgumentsProvider
+import org.junit.jupiter.params.provider.ArgumentsSource
+import ru.romanow.models.buildTreeFromList
+import ru.romanow.models.printTree
+import java.util.stream.Stream
+
+class InOrderDeepFirstSearchTest {
+
+    @ArgumentsSource(ValueProvider::class)
+    @ParameterizedTest(name = "#{index} – In-order dfs {0} is {1}")
+    fun flatten(items: List<Int?>, result: List<Int>) {
+        val root = buildTreeFromList(items)
+        printTree(root)
+
+        val obj = InOrderDeepFirstSearch()
+        assertThat(obj.traverse(root)).isEqualTo(result)
+    }
+
+    internal class ValueProvider : ArgumentsProvider {
+        override fun provideArguments(context: ExtensionContext): Stream<Arguments> =
+            Stream.of(Arguments.of(listOf(10, 5, 15, 3, 7, 12, 20), listOf(3, 5, 7, 10, 12, 15, 20)))
+    }
+}