Linked list (#915)

Author: A-O-Emmanuel

bin/auto-sync.txt

@@ -39,6 +39,7 @@ knapsack
 largest-series-product
 leap
 list-ops
+linked-list
 luhn
 matching-brackets
 meetup

exercises/practice/linked-list/.meta/config.json

@@ -2,6 +2,9 @@
   "authors": [
     "MichaelBunker"
   ],
+  "contributors": [
+    "A-O-Emmanuel"
+  ],
   "files": {
     "solution": [
       "LinkedList.php"
@@ -13,5 +16,6 @@
       ".meta/example.php"
     ]
   },
-  "blurb": "Implement a doubly linked list"
+  "blurb": "Implement a doubly linked list.",
+  "source": "Classic computer science topic"
 }

exercises/practice/linked-list/.meta/example.php

@@ -1,27 +1,5 @@
 <?php
 
-/*
- * By adding type hints and enabling strict type checking, code can become
- * easier to read, self-documenting and reduce the number of potential bugs.
- * By default, type declarations are non-strict, which means they will attempt
- * to change the original type to match the type specified by the
- * type-declaration.
- *
- * In other words, if you pass a string to a function requiring a float,
- * it will attempt to convert the string value to a float.
- *
- * To enable strict mode, a single declare directive must be placed at the top
- * of the file.
- * This means that the strictness of typing is configured on a per-file basis.
- * This directive not only affects the type declarations of parameters, but also
- * a function's return type.
- *
- * For more info review the Concept on strict type checking in the PHP track
- * <link>.
- *
- * To disable strict typing, comment out the directive below.
- */
-
 declare(strict_types=1);
 
 class LinkedList
@@ -71,6 +49,50 @@ public function shift()
 
         return $data;
     }
+
+    public function count(): int
+    {
+        if (!$this->head) {
+            return 0;
+        }
+
+        $count = 1;
+        $current = $this->head->next;
+
+        while ($current !== $this->head) {
+            $count++;
+            $current = $current->next;
+        }
+
+        return $count;
+    }
+
+    public function delete($value): void
+    {
+        if (!$this->head) {
+            return;
+        }
+
+        $current = $this->head;
+        do {
+            if ($current->data === $value) {
+                if ($current->next === $current) {
+                    $this->head = null;
+                    return;
+                }
+
+                $current->prev->next = $current->next;
+                $current->next->prev = $current->prev;
+
+                if ($current === $this->head) {
+                    $this->head = $current->next;
+                }
+
+                return;
+            }
+            $current = $current->next;
+        } while ($current !== $this->head);
+    }
 }
 
 class Node

exercises/practice/linked-list/.meta/tests.toml

@@ -0,0 +1,67 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[7f7e3987-b954-41b8-8084-99beca08752c]
+description = "pop gets element from the list"
+
+[c3f67e5d-cfa2-4c3e-a18f-7ce999c3c885]
+description = "push/pop respectively add/remove at the end of the list"
+
+[00ea24ce-4f5c-4432-abb4-cc6e85462657]
+description = "shift gets an element from the list"
+
+[37962ee0-3324-4a29-b588-5a4c861e6564]
+description = "shift gets first element from the list"
+
+[30a3586b-e9dc-43fb-9a73-2770cec2c718]
+description = "unshift adds element at start of the list"
+
+[042f71e4-a8a7-4cf0-8953-7e4f3a21c42d]
+description = "pop, push, shift, and unshift can be used in any order"
+
+[88f65c0c-4532-4093-8295-2384fb2f37df]
+description = "count an empty list"
+
+[fc055689-5cbe-4cd9-b994-02e2abbb40a5]
+description = "count a list with items"
+
+[8272cef5-130d-40ea-b7f6-5ffd0790d650]
+description = "count is correct after mutation"
+
+[229b8f7a-bd8a-4798-b64f-0dc0bb356d95]
+description = "popping to empty doesn't break the list"
+
+[4e1948b4-514e-424b-a3cf-a1ebbfa2d1ad]
+description = "shifting to empty doesn't break the list"
+
+[e8f7c600-d597-4f79-949d-8ad8bae895a6]
+description = "deletes the only element"
+
+[fd65e422-51f3-45c0-9fd0-c33da638f89b]
+description = "deletes the element with the specified value from the list"
+
+[59db191a-b17f-4ab7-9c5c-60711ec1d013]
+description = "deletes the element with the specified value from the list, re-assigns tail"
+
+[58242222-5d39-415b-951d-8128247f8993]
+description = "deletes the element with the specified value from the list, re-assigns head"
+
+[ee3729ee-3405-4bd2-9bad-de0d4aa5d647]
+description = "deletes the first of two elements"
+
+[47e3b3b4-b82c-4c23-8c1a-ceb9b17cb9fb]
+description = "deletes the second of two elements"
+
+[7b420958-f285-4922-b8f9-10d9dcab5179]
+description = "delete does not modify the list if the element is not found"
+
+[7e04828f-6082-44e3-a059-201c63252a76]
+description = "deletes only the first occurrence"