Added insert after specific node functionality to Linked List

Author: Alienpruts

chap-03/linked-lists.php

@@ -13,7 +13,7 @@
 $bookTitles = new LinkedList();
 
 // Insert three books
-$bookTitles->insert("Introduction to Algortihms");
+$bookTitles->insert("Introduction to Algorithms");
 $bookTitles->insert("Introduction to PHP Data Structures");
 $bookTitles->insert("Programming Intelligence");
 
@@ -29,7 +29,12 @@
 var_dump($bookTitles->search("Introducing PHP to noobs")->data);
 var_dump($bookTitles->search("Clever stuff"));
 
-// Insert a title befor another title
+// Insert a title before another title
 $bookTitles->insertBefore("Handsome developers", "Programming Intelligence");
 
+$bookTitles->display();
+
+// Insert a title after another title
+$bookTitles->insertAfter("The complex anatomy of a developer", "Introduction to Algorithms");
+
 $bookTitles->display();

src/Chapter03/LinkedList.php

@@ -93,7 +93,7 @@ public function search(string $data = NULL)
      * @param string|null $data
      * @param string|null $query
      */
-    public function insertBefore(string $data = null, string $query = null)
+    public function insertBefore(string $data = NULL, string $query = NULL)
     {
         $newNode = new ListNode($data);
 
@@ -113,4 +113,35 @@ public function insertBefore(string $data = null, string $query = null)
         }
     }
 
+    /**
+     * Inserts a new node before an existing node.
+     * Care must be taken to set the next values of the node after and the searched node itself
+     * @param string|null $data
+     * @param string|null $query
+     */
+    public function insertAfter(string $data = NULL, string $query = NULL)
+    {
+        $newNode = new ListNode($data);
+
+        if ($this->_firstNode) {
+            $nextNode = NULL;
+            $currentNode = $this->_firstNode;
+            while ($currentNode !== NULL) {
+                if ($currentNode->data === $query) {
+                    if ($nextNode !== NULL) {
+                        $newNode->next = $nextNode;
+                    }
+                    $currentNode->next = $newNode;
+                    $this->_totalNodes++;
+                    break;
+                }
+                $currentNode = $currentNode->next;
+                // We can only set the next Node if a value exists for next in the current node.
+                if (isset($currentNode->next)) {
+                    $nextNode = $currentNode->next;
+                }
+            }
+        }
+    }
+
 }