recuurent algorithm for comparing binary trees

Author: Michał Żarnecki

DIRECTORY.md

@@ -27,6 +27,9 @@
     * [Bstnode](./DataStructures/BinarySearchTree/BSTNode.php)
     * [Bstree](./DataStructures/BinarySearchTree/BSTree.php)
     * [Duplicatekeyexception](./DataStructures/BinarySearchTree/DuplicateKeyException.php)
+  * CompareBinaryTree
+    * [CompareBinaryTree](./DataStructures/CompareBinaryTree/CompareBinaryTree.php)
+    * [Node](./DataStructures/CompareBinaryTree/Node.php)
   * Disjointsets
     * [Disjointset](./DataStructures/DisjointSets/DisjointSet.php)
     * [Disjointsetnode](./DataStructures/DisjointSets/DisjointSetNode.php)
@@ -50,6 +53,7 @@
   * [Bellmanford](./Graphs/BellmanFord.php)
   * [Breadthfirstsearch](./Graphs/BreadthFirstSearch.php)
   * [Depthfirstsearch](./Graphs/DepthFirstSearch.php)
+  * [Dijkstra's](./Graphs/Dijkstras.php)
 
 ## Maths
   * [Absolutemax](./Maths/AbsoluteMax.php)

DataStructures/CompareBinaryTree/CompareBinaryTree.php

@@ -0,0 +1,34 @@
+<?php
+namespace DataStructures\CompareBinaryTree;
+
+/**
+ * Recurrent comparison of binary trees based on comparison of left and right branches
+ * (https://en.wikipedia.org/wiki/Binary_tree).
+ *
+ * @author Michał Żarnecki https://github.com/rzarno
+ */
+class CompareBinaryTree
+{
+    /**
+     * compare two binary trees
+     * @param Node|null $a
+     * @param Node|null $b
+     * @return bool
+     */
+    public function areTreesEqual(?Node $a, ?Node $b): bool
+    {
+        if (! $a  &&  $b || $a && ! $b) {
+            return false;
+        }
+
+        if (! $a && ! $b) {
+            return true;
+        }
+
+        if ($a->value !== $b->value) {
+            return false;
+        }
+        return  $this->areTreesEqual($a->left, $b->left)
+            &&  $this->areTreesEqual($a->right, $b->right);
+    }
+}

DataStructures/CompareBinaryTree/Node.php

@@ -0,0 +1,16 @@
+<?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;
+}

tests/DataStructures/CompareBinaryTreeTest.php

@@ -0,0 +1,91 @@
+<?php
+
+namespace DataStructures;
+
+require_once __DIR__ . '/../../vendor/autoload.php';
+require_once __DIR__ . '/../../DataStructures/CompareBinaryTree/Node.php';
+require_once __DIR__ . '/../../DataStructures/CompareBinaryTree/CompareBinaryTree.php';
+
+use DataStructures\CompareBinaryTree\CompareBinaryTree;
+use DataStructures\CompareBinaryTree\Node;
+use PHPUnit\Framework\TestCase;
+
+class CompareBinaryTreeTest extends TestCase
+{
+    public function testBinaryTreesAreEqualWhenAreEqualInReality()
+    {
+        $tree1 = new Node(
+            'A',
+            new Node(
+                'B',
+                new Node(
+                    'D'
+                ),
+                new Node(
+                    'E',
+                    null,
+                    new Node(
+                        'F'
+                    )
+                )
+            ),
+            new Node(
+                'C',
+                new Node('G')
+            )
+        );
+
+        $tree2 = clone $tree1;
+
+        $sut = new CompareBinaryTree();
+        $this->assertTrue($sut->areTreesEqual($tree1, $tree2));
+    }
+
+    public function testBinaryTreesAreNotEqualWhenAreNotEqualInReality()
+    {
+
+        $tree1 = new Node(
+            'A',
+            new Node(
+                'B',
+                new Node(
+                    'F'
+                ),
+                new Node(
+                    'E',
+                    null,
+                    new Node(
+                        'D'
+                    )
+                )
+            ),
+            new Node(
+                'C',
+                new Node('G')
+            )
+        );
+
+        $tree2 = new Node(
+            'A',
+            new Node(
+                'B',
+                new Node(
+                    'F'
+                ),
+                new Node(
+                    'E',
+                    null,
+                    new Node(
+                        'D'
+                    )
+                )
+            ),
+            new Node(
+                'C'
+            )
+        );
+
+        $sut = new CompareBinaryTree();
+        $this->assertFalse($sut->areTreesEqual($tree1, $tree2));
+    }
+}