Trie wordCount, LinkedList intersectionNode

Author: doganoo

src/Common/Abstracts/AbstractLinkedList.php

@@ -26,6 +26,7 @@
 namespace doganoo\PHPAlgorithms\Common\Abstracts;
 
 use doganoo\PHPAlgorithms\Common\Interfaces\IComparable;
+use doganoo\PHPAlgorithms\Common\Interfaces\INode;
 use doganoo\PHPAlgorithms\Common\Interfaces\IUnaryNode;
 use doganoo\PHPAlgorithms\Common\Util\Comparator;
 use doganoo\PHPAlgorithms\Datastructure\Lists\Node;
@@ -285,27 +286,6 @@ public abstract function prepend(?Node $node): bool;
     //    return $list;
     //}
 
-    /**
-     * returns the number of elements in a list
-     *
-     * @return int
-     */
-    public function size() {
-        if ($this->isEmpty()) {
-            return 0;
-        }
-        return $this->head->size();
-    }
-
-    /**
-     * if the list is empty or not
-     *
-     * @return bool
-     */
-    public function isEmpty() {
-        return $this->head == null;
-    }
-
     /**
      * adds a Node instance to the list
      *
@@ -537,6 +517,76 @@ public function getMiddleNode(): ?IUnaryNode {
         return $p;
     }
 
+    public function getIntersectionNode(AbstractLinkedList $list): ?INode {
+        if (0 === $this->size()) return null;
+        if (0 === $list->size()) return null;
+
+        $l1 = $this->getHead();
+        $l2 = $list->getHead();
+
+        $c1 = 0;
+        $c2 = 0;
+
+        while (null !== $l1) {
+            $c1++;
+            $l1 = $l1->getNext();
+        }
+
+        while (null !== $l2) {
+            $c2++;
+            $l2 = $l2->getNext();
+        }
+
+        $l1 = $this->getHead();
+        $l2 = $list->getHead();
+
+        if ($c1 > $c2) {
+            $len = $c1 - $c2;
+            while ($len > 0) {
+                $l1 = $l1->getNext();
+                $len--;
+            }
+        } else {
+            $len = $c2 - $c1;
+            while ($len > 0) {
+                $l2 = $l2->getNext();
+                $len--;
+            }
+        }
+
+
+        while (null !== $l1 && null !== $l2) {
+            if ($l1 == $l2) {
+                return $l1;
+            }
+            $l1 = $l1->getNext();
+            $l2 = $l2->getNext();
+        }
+
+        return null;
+    }
+
+    /**
+     * returns the number of elements in a list
+     *
+     * @return int
+     */
+    public function size() {
+        if ($this->isEmpty()) {
+            return 0;
+        }
+        return $this->head->size();
+    }
+
+    /**
+     * if the list is empty or not
+     *
+     * @return bool
+     */
+    public function isEmpty() {
+        return $this->head == null;
+    }
+
     /**
      * Specify data which should be serialized to JSON
      *

src/Datastructure/Graph/Tree/Trie/Node.php

@@ -83,7 +83,7 @@ public function createEndOfWordNode() {
      * indicates whether it is the end of the node
      * @return bool
      */
-    public function isEndOfNode() {
+    public function isEndOfWordNode() {
         return $this->children[0] instanceof EndOfWordNode;
     }
 

src/Datastructure/Graph/Tree/Trie/Trie.php

@@ -35,6 +35,10 @@
  * @package doganoo\PHPAlgorithms\Datastructure\Trie
  */
 class Trie implements IComparable, \JsonSerializable {
+    /**
+     * number of characters in english alphabet
+     */
+    public const ALPHABET_SIZE = 26;
     /**
      * @var RootNode
      */
@@ -97,7 +101,7 @@ public function search(string $key, bool $isPrefix = false): bool {
         if ($isPrefix) {
             return null !== $node;
         } else {
-            return (null !== $node && $node->isEndOfNode());
+            return (null !== $node && $node->isEndOfWordNode());
         }
     }
 
@@ -114,6 +118,34 @@ public function compareTo($object): int {
         return -1;
     }
 
+    /**
+     * returns the number of words in the trie
+     *
+     * @return int
+     */
+    public function countWords(): int {
+        return $this->_countWords($this->root);
+    }
+
+    /**
+     * helper method for counting number of words in the trie
+     *
+     * @param Node $node
+     * @return int
+     */
+    private function _countWords(?Node $node): int {
+        $result = 0;
+        if (null === $node) return $result;
+        if ($node->isEndOfWordNode()) $result++;
+        for ($i = 0; $i < self::ALPHABET_SIZE; $i++) {
+            if ($node->hasChild($i)) {
+                $child = $node->getChildNode($i);
+                $result += $this->_countWords($child);
+            }
+        }
+        return $result;
+    }
+
     /**
      * Specify data which should be serialized to JSON
      *

tests/Graph/trees/trie/TrieTest.php

@@ -23,6 +23,8 @@
  * SOFTWARE.
  */
 
+use doganoo\PHPAlgorithms\Datastructure\Graph\Tree\Trie\Trie;
+
 /**
  * Class TrieTest
  */
@@ -31,12 +33,25 @@ class TrieTest extends \PHPUnit\Framework\TestCase {
      * tests inserting and searching
      */
     public function testAdd() {
-        $trie = new \doganoo\PHPAlgorithms\Datastructure\Graph\Tree\Trie\Trie();
+        $trie = new Trie();
         $trie->insert("Test");
         $found = $trie->search("Test");
         $this->assertTrue($found === true);
         $found = $trie->search("Te", true);
         $this->assertTrue($found === true);
     }
 
+    public function testWordCount() {
+        $trie = new Trie();
+        $trie->insert("this");
+        $trie->insert("is");
+        $trie->insert("a");
+        $trie->insert("very");
+        $trie->insert("long");
+        $trie->insert("word");
+
+        $this->assertTrue(6 === $trie->countWords());
+        $this->assertTrue(6 === $trie->getAllWords()->size());
+    }
+
 }