implementation of algorithms: 1. compare binary trees, 2. inverse binary tree, 3. reverse linked list

DIRECTORY.md

@@ -28,14 +28,20 @@
     * [Bstree](./DataStructures/BinarySearchTree/BSTree.php)
     * [Duplicatekeyexception](./DataStructures/BinarySearchTree/DuplicateKeyException.php)
   * CompareBinaryTree
-    * [CompareBinaryTree](./DataStructures/CompareBinaryTree/CompareBinaryTree.php)
-    * [Node](./DataStructures/CompareBinaryTree/Node.php)
+    * [CompareBinaryTree](./DataStructures/CompareBinaryTree.php)
+    * [BinaryTreeNode](./DataStructures/BinaryTreeNode.php)
   * Disjointsets
     * [Disjointset](./DataStructures/DisjointSets/DisjointSet.php)
     * [Disjointsetnode](./DataStructures/DisjointSets/DisjointSetNode.php)
   * [Doublylinkedlist](./DataStructures/DoublyLinkedList.php)
+  * InvertBinaryTree
+    * [InvertBinaryTree](./DataStructures/InvertBinaryTree.php)
+    * [BinaryTree](./DataStructures/BinaryTree.php)
   * [Node](./DataStructures/Node.php)
   * [Queue](./DataStructures/Queue.php)
+  * ReverseLinkedList
+    * [ReverseLinkedList.php](DataStructures/ReverseLinkedList.php)
+    * [LinkedListItem.php](DataStructures/LinkedListItem.php)
   * Segmenttree
     * [Segmenttree](./DataStructures/SegmentTree/SegmentTree.php)
     * [Segmenttreenode](./DataStructures/SegmentTree/SegmentTreeNode.php)

DataStructures/BinaryTree.php

@@ -0,0 +1,40 @@
+<?php
+
+class BinaryTree {
+    private ?BinaryTree $left = null;
+    private ?BinaryTree $right = null;
+    private $value;
+
+    public function setLeft(?BinaryTree $left)
+    {
+        $this->left = $left;
+        return $this;
+    }
+
+    public function getLeft(): ?BinaryTree
+    {
+        return $this->left;
+    }
+
+    public function setRight(?BinaryTree $right)
+    {
+        $this->right = $right;
+        return $this;
+    }
+
+    public function getRight(): ?BinaryTree
+    {
+        return $this->right;
+    }
+
+    public function setValue($value)
+    {
+        $this->value = $value;
+        return $this;
+    }
+
+    public function getValue()
+    {
+        return $this->value;
+    }
+}

DataStructures/BinaryTreeNode.php

@@ -0,0 +1,16 @@
+<?php
+namespace DataStructures;
+
+class BinaryTreeNode
+{
+    public function __construct($value, ?BinaryTreeNode $left = null, BinaryTreeNode $right = null)
+    {
+        $this->value = $value;
+        $this->left = $left;
+        $this->right = $right;
+    }
+
+    public $value;
+    public ?BinaryTreeNode $left;
+    public ?BinaryTreeNode $right;
+}

DataStructures/CompareBinaryTree.php

@@ -1,5 +1,6 @@
 <?php
-namespace DataStructures\CompareBinaryTree;
+
+namespace DataStructures;
 
 /**
  * Recurrent comparison of binary trees based on comparison of left and right branches
@@ -11,11 +12,11 @@ class CompareBinaryTree
 {
     /**
      * compare two binary trees
-     * @param Node|null $a
-     * @param Node|null $b
+     * @param BinaryTreeNode|null $a
+     * @param BinaryTreeNode|null $b
      * @return bool
      */
-    public function areTreesEqual(?Node $a, ?Node $b): bool
+    public function areTreesEqual(?BinaryTreeNode $a, ?BinaryTreeNode $b): bool
     {
         if (! $a  &&  $b || $a && ! $b) {
             return false;

DataStructures/CompareBinaryTree/Node.php

@@ -1,16 +0,0 @@
-<?php
-namespace DataStructures\CompareBinaryTree;
-
-class Node
-{
-    public function __construct($value, ?Node $left = null, Node $right = null)
-    {
-        $this->value = $value;
-        $this->left = $left;
-        $this->right = $right;
-    }
-
-    public $value;
-    public ?Node $left;
-    public ?Node $right;
-}

DataStructures/InvertBinaryTree.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace DataStructures;
+
+use BinaryTree;
+
+/**
+ * Recurrent algorithm to invert binary tree (mirror)
+ * (https://medium.com/@kvrware/inverting-binary-tree-b0ff3a5cb0df).
+ *
+ * @author Michał Żarnecki https://github.com/rzarno
+ */
+class InvertBinaryTree
+{
+    public function invert(?BinaryTree $b): void
+    {
+        if (! $b) {
+            return;
+        }
+        $tmp = $b->getLeft();
+        $b->setLeft($b->getRight());
+        $b->setRight($tmp);
+        $this->invert($b->getLeft());
+        $this->invert($b->getRight());
+    }
+}

DataStructures/LinkedListItem.php

@@ -0,0 +1,40 @@
+<?php
+
+class LinkedListItem {
+    private ?LinkedListItem $next = null;
+    private ?LinkedListItem $prev = null;
+    private $value;
+
+    public function setNext(?LinkedListItem $next)
+    {
+        $this->next = $next;
+        return $this;
+    }
+
+    public function getNext(): ?LinkedListItem
+    {
+        return $this->next;
+    }
+
+    public function setPrev(?LinkedListItem $prev)
+    {
+        $this->prev = $prev;
+        return $this;
+    }
+
+    public function getPrev(): ?LinkedListItem
+    {
+        return $this->prev;
+    }
+
+    public function setValue($value)
+    {
+        $this->value = $value;
+        return $this;
+    }
+
+    public function getValue()
+    {
+        return $this->value;
+    }
+}

DataStructures/ReverseLinkedList.php

@@ -0,0 +1,26 @@
+<?php
+
+/**
+ * Reverse linked list
+ * (https://en.wikipedia.org/wiki/Linked_list).
+ *
+ * @author Michał Żarnecki https://github.com/rzarno
+ */
+class ReverseLinkedList
+{
+    public function reverse(LinkedListItem $item): LinkedListItem
+    {
+        $next = $item->getNext();
+        $item->setNext(null);
+        while (true) {
+            $item->setPrev($next);
+            if (! $next) {
+                return $item;
+            }
+            $nextNext = $next->getNext();
+            $next->setNext($item);
+            $item = $next;
+            $next = $nextNext;
+        }
+    }
+}

tests/DataStructures/CompareBinaryTreeTest.php

@@ -3,35 +3,33 @@
 namespace DataStructures;
 
 require_once __DIR__ . '/../../vendor/autoload.php';
-require_once __DIR__ . '/../../DataStructures/CompareBinaryTree/Node.php';
-require_once __DIR__ . '/../../DataStructures/CompareBinaryTree/CompareBinaryTree.php';
+require_once __DIR__ . '/../../DataStructures/BinaryTreeNode.php';
+require_once __DIR__ . '/../../DataStructures/CompareBinaryTree.php';
 
-use DataStructures\CompareBinaryTree\CompareBinaryTree;
-use DataStructures\CompareBinaryTree\Node;
 use PHPUnit\Framework\TestCase;
 
 class CompareBinaryTreeTest extends TestCase
 {
     public function testBinaryTreesAreEqualWhenAreEqualInReality()
     {
-        $tree1 = new Node(
+        $tree1 = new BinaryTreeNode(
             'A',
-            new Node(
+            new BinaryTreeNode(
                 'B',
-                new Node(
+                new BinaryTreeNode(
                     'D'
                 ),
-                new Node(
+                new BinaryTreeNode(
                     'E',
                     null,
-                    new Node(
+                    new BinaryTreeNode(
                         'F'
                     )
                 )
             ),
-            new Node(
+            new BinaryTreeNode(
                 'C',
-                new Node('G')
+                new BinaryTreeNode('G')
             )
         );
 
@@ -44,43 +42,43 @@ class CompareBinaryTreeTest extends TestCase
     public function testBinaryTreesAreNotEqualWhenAreNotEqualInReality()
     {
 
-        $tree1 = new Node(
+        $tree1 = new BinaryTreeNode(
             'A',
-            new Node(
+            new BinaryTreeNode(
                 'B',
-                new Node(
+                new BinaryTreeNode(
                     'F'
                 ),
-                new Node(
+                new BinaryTreeNode(
                     'E',
                     null,
-                    new Node(
+                    new BinaryTreeNode(
                         'D'
                     )
                 )
             ),
-            new Node(
+            new BinaryTreeNode(
                 'C',
-                new Node('G')
+                new BinaryTreeNode('G')
             )
         );
 
-        $tree2 = new Node(
+        $tree2 = new BinaryTreeNode(
             'A',
-            new Node(
+            new BinaryTreeNode(
                 'B',
-                new Node(
+                new BinaryTreeNode(
                     'F'
                 ),
-                new Node(
+                new BinaryTreeNode(
                     'E',
                     null,
-                    new Node(
+                    new BinaryTreeNode(
                         'D'
                     )
                 )
             ),
-            new Node(
+            new BinaryTreeNode(
                 'C'
             )
         );

tests/DataStructures/InvertBinaryTreeTest.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace DataStructures;
+
+require_once __DIR__ . '/../../vendor/autoload.php';
+require_once __DIR__ . '/../../DataStructures/BinaryTree.php';
+require_once __DIR__ . '/../../DataStructures/InvertBinaryTree.php';
+
+use BinaryTree;
+use PHPUnit\Framework\TestCase;
+
+class InvertBinaryTreeTest extends TestCase
+{
+    public function testInvertBinaryTree()
+    {
+        $b = (new BinaryTree())->setValue(1);
+        $bl = (new BinaryTree())->setValue(3);
+        $b->setLeft($bl);
+        $br = (new BinaryTree())->setValue(2);
+        $b->setRight($br);
+        $br->setLeft((new BinaryTree())->setValue(4));
+        $br->setRight((new BinaryTree())->setValue(5));
+
+        $expected = (new BinaryTree())->setValue(1);
+        $expectedBr = (new BinaryTree())->setValue(3);
+        $expected->setRight($expectedBr);
+        $expectedBl = (new BinaryTree())->setValue(2);
+        $expected->setLeft($expectedBl);
+        $expectedBl->setRight((new BinaryTree())->setValue(4));
+        $expectedBl->setLeft((new BinaryTree())->setValue(5));
+
+        (new InvertBinaryTree())->invert($b);
+
+        $this->assertEquals($expected, $b);
+    }
+}

tests/DataStructures/ReverseLinkedListTest.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace DataStructures;
+
+require_once __DIR__ . '/../../vendor/autoload.php';
+require_once __DIR__ . '/../../DataStructures/LinkedListItem.php';
+require_once __DIR__ . '/../../DataStructures/ReverseLinkedList.php';
+
+use LinkedListItem;
+use ReverseLinkedList;
+use PHPUnit\Framework\TestCase;
+
+class ReverseLinkedListTest extends TestCase
+{
+    public function testReverseLinkedList()
+    {
+        $list = [1,2,3,4,5];
+
+        $firstItem = (new LinkedListItem())->setValue(0);
+
+        $prevItem = $firstItem;
+
+        foreach ($list as $value) {
+            $item = new LinkedListItem();
+            $item->setValue($value);
+            $item->setPrev($prevItem);
+            $prevItem->setNext($item);
+            $prevItem = $item;
+        }
+
+        $newFirstItem = (new ReverseLinkedList())->reverse($firstItem);
+        do {
+            $this->assertEquals($newFirstItem->getValue(), array_pop($list));
+        } while ($newFirstItem = $newFirstItem->getNext());
+    }
+}