Added tree ds; with BST inside

Author: gedex

data_structure/tree/binary_search_tree.php

@@ -0,0 +1,190 @@
+<?php
+
+class Node {
+  private $_val;
+
+  /**
+   * Parent's node.
+   * @access private
+   * @type Node
+   */
+  private $_parent;
+
+  /**
+   * Left-child's node.
+   * @access private
+   * @type Node
+   */
+  private $_left;
+
+  /**
+   * Right-child's node.
+   * @access private
+   * @type Node
+   */
+  private $_right;
+
+  public function __construct($el) {
+    $this->_val = $el;
+  }
+
+  /**
+   * Get node's value.
+   * @access public
+   * @return Node
+   */
+  public function val() {
+    return $this->_val;
+  }
+
+  /**
+   * Get left-child's node.
+   * @access public
+   * @return Node
+   */
+  public function left() {
+    return $this->_left;
+  }
+
+  /**
+   * Set left-child's node.
+   * @access public
+   * @return void
+   */
+  public function setLeft(Node $node) {
+    $this->_left = $node;
+  }
+
+  /**
+   * Get right-child's node.
+   * @access public
+   * @return Node
+   */
+  public function right() {
+    return $this->_right;
+  }
+
+  /**
+   * Set right-child's node.
+   * @access public
+   * @return void
+   */
+  public function setRight(Node $node) {
+    $this->_right = $node;
+  }
+
+  /**
+   * Get parent's node.
+   * @access public
+   * @return Node
+   */
+  public function parent() {
+    return $this->_parent;
+  }
+
+  /**
+   * Set parent's node.
+   * @access public
+   * @return public
+   */
+  public function setParent(Node $node) {
+    $this->_parent = $node;
+  }
+
+  public function __toString() {
+    return $this->val() === NULL ? 'NULL' : $this->val() . '';
+  }
+}
+
+class BinarySearchTree {
+  private $_root;
+  private $_sentinel;
+
+  public function __construct() {
+    $this->_sentinel = new Node(NULL);
+
+    $this->_root = $this->_sentinel;
+    $this->_root->setParent($this->_sentinel);
+    $this->_root->setLeft($this->_sentinel);
+    $this->_root->setRight($this->_sentinel);
+  }
+
+  public function insert($val) {
+    if (!is_object($val) || getclass($val) !== 'Node') {
+      $newNode = new Node($val);
+    } else {
+      $newNode = $val;
+    }
+    $newNode->setLeft($this->_sentinel);
+    $newNode->setRight($this->_sentinel);
+
+    $node = $this->_root;
+    $parent = $this->_sentinel;
+    while ($node !== $this->_sentinel) {    
+      $parent = $node;
+      if ($newNode->val() < $node->val()) {
+        $node = $node->left();
+      } else {
+        $node = $node->right();
+      }
+    }
+
+    if ($parent === $this->_sentinel) {
+      $newNode->setParent($this->_sentinel);
+      $this->_root = $newNode;
+    } else {
+      if ($newNode->val() < $parent->val()) {
+        $parent->setLeft($newNode);
+      } else {
+        $parent->setRight($newNode);
+      }
+      $newNode->setParent($parent);
+    }
+  }
+
+  public function search($val) {
+    $node = $this->_root;
+
+    while ($node !== $this->_sentinel && $node->val() !== $val) {
+      if ($val < $node->val()) {
+        $node = $node->left();
+      } else {
+        $node = $node->right();
+      }
+    }
+    return $node;
+  }
+}
+
+$BST = new BinarySearchTree;
+$BST->insert(15);
+$BST->insert(6);
+$BST->insert(18);
+$BST->insert(3);
+$BST->insert(7);
+$BST->insert(17);
+$BST->insert(20);
+$BST->insert(2);
+$BST->insert(4);
+$BST->insert(13);
+$BST->insert(9);
+
+function test_searching($num) {
+  global $BST;
+
+  $node = $BST->search($num);
+  if ($node->val() !== NULL) {
+    echo "Node with value $num is found\n";
+    echo "Parent's node = " . $node->parent() . "\n";
+    echo "Left-child's node = " . $node->left() . "\n";
+    echo "Right-child's node = " . $node->right() . "\n";
+  } else {
+    echo "Node with value $num is NOT found\n";
+  }
+  echo "\n";
+}
+
+test_searching(7);
+test_searching(15);
+test_searching(3);
+test_searching(2);