[simple-linked-list] Add new practice exercise

config.json

@@ -471,6 +471,14 @@
         "prerequisites": [],
         "difficulty": 5
       },
+      {
+        "slug": "simple-linked-list",
+        "name": "Simple Linked List",
+        "uuid": "4a6222cd-3fd8-4f6b-8472-ec9c0696d492",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 5
+      },
       {
         "slug": "sum-of-multiples",
         "name": "Sum of Multiples",

exercises/practice/simple-linked-list/.docs/instructions.md

@@ -0,0 +1,19 @@
+# Instructions
+
+Write a prototype of the music player application.
+
+For the prototype, each song will simply be represented by a number.
+Given a range of numbers (the song IDs), create a singly linked list.
+
+Given a singly linked list, you should be able to reverse the list to play the songs in the opposite order.
+
+~~~~exercism/note
+The linked list is a fundamental data structure in computer science, often used in the implementation of other data structures.
+
+The simplest kind of linked list is a **singly** linked list.
+That means that each element (or "node") contains data, along with something that points to the next node in the list.
+
+If you want to dig deeper into linked lists, check out [this article][intro-linked-list] that explains it using nice drawings.
+
+[intro-linked-list]: https://medium.com/basecs/whats-a-linked-list-anyway-part-1-d8b7e6508b9d
+~~~~

exercises/practice/simple-linked-list/.docs/introduction.md

@@ -0,0 +1,5 @@
+# Introduction
+
+You work for a music streaming company.
+
+You've been tasked with creating a playlist feature for your music player application.

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

@@ -0,0 +1,22 @@
+{
+  "authors": [
+    "IsaacG"
+  ],
+  "files": {
+    "solution": [
+      "simple_linked_list.gd"
+    ],
+    "test": [
+      "simple_linked_list_test.gd",
+      "run_tests",
+      "lib/test_runner.gd",
+      "project.godot"
+    ],
+    "example": [
+      ".meta/example.gd"
+    ]
+  },
+  "blurb": "Write a simple linked list implementation that uses Elements and a List.",
+  "source": "Inspired by 'Data Structures and Algorithms with Object-Oriented Design Patterns in Ruby', singly linked-lists.",
+  "source_url": "https://web.archive.org/web/20160731005714/http://brpreiss.com/books/opus8/html/page96.html"
+}

exercises/practice/simple-linked-list/.meta/example.gd

@@ -0,0 +1,56 @@
+class ListNode:
+
+	var value = 0
+	var next = null
+
+	func _init(value, next = null):
+		self.value = value
+		self.next = next
+
+
+class LinkedList:
+
+	var _head = null
+
+	func _init(values):
+		for value in values:
+			push(value)
+
+	func count():
+		var cur = _head
+		var count = 0
+		while cur != null:
+			count += 1
+			cur = cur.next
+		return count
+
+	func push(value):
+		_head = ListNode.new(value, _head)
+
+	func peek():
+		if _head == null:
+			return null
+		return _head.value
+
+	func pop():
+		if _head == null:
+			return null
+		var out = _head.value
+		_head = _head.next
+		return out
+
+	func to_list():
+		var values = []
+		var cur = _head
+		while cur != null:
+			values.append(cur.value)
+			cur = cur.next
+		values.reverse()
+		return values
+
+	func reverse():
+		var values = to_list()
+		values.reverse()
+		_head = null
+		for value in values:
+			push(value)

exercises/practice/simple-linked-list/.meta/template.j2

@@ -0,0 +1,38 @@
+{% for case in cases %}
+func test_{{ case.func_name }}(solution_script):
+	var linked_list = solution_script.LinkedList.new({{ case.input.initialValues | togdscript }})
+	var res = 0
+{% for op in case.input.operations %}
+{%- if op.operation == "count" %}
+	res = linked_list.count()
+	if res != {{ op.expected }}:
+		return [false, "count() = %d; expected %d" % [res, {{ op.expected }}]]
+{%- elif op.operation == "pop" and op.expected is sequence %}
+	res = linked_list.pop()
+	if res != null:
+		return [false, "pop() = %d; expected null" % res]
+{%- elif op.operation == "pop" %}
+	res = linked_list.pop()
+	if res != {{ op.expected }}:
+		return [false, "pop() = %d; expected %d" % [res, {{ op.expected }}]]
+{%- elif op.operation == "push" %}
+	linked_list.push({{ op.value }})
+{%- elif op.operation == "peek" and op.expected is sequence %}
+	res = linked_list.peek()
+	if res != null:
+		return [false, "peek() = %d, expected null" % res]
+{%- elif op.operation == "peek" %}
+	res = linked_list.peek()
+	if res != {{ op.expected }}:
+		return [false, "peek() = %d; expected %d" % [res, {{ op.expected }}]]
+{%- elif op.operation == "toList" %}
+	res = linked_list.to_list()
+	if res != {{ op.expected | togdscript }}:
+		return [false, "to_list() = %s; expected %s" % [res, {{ op.expected | togdscript }}]]
+{%- else %}
+	linked_list.{{ op.operation }}()
+{%- endif %}
+{% endfor %}
+	return [true, true]
+
+{% endfor %}

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

@@ -0,0 +1,107 @@
+# 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.
+
+[962d998c-c203-41e2-8fbd-85a7b98b79b9]
+description = "count -> Empty list has length of zero"
+
+[9760262e-d7e4-4639-9840-87e2e2fbb115]
+description = "count -> Singleton list has length of one"
+
+[d9955c90-637c-441b-b41d-8cfb48e924a8]
+description = "count -> Non-empty list has correct length"
+
+[0c3966db-58f9-4632-b94c-8ea13e54c2c8]
+description = "pop -> Pop from empty list is an error"
+
+[a4f9d2e1-7425-49ef-9ee8-6c0cb3407cf0]
+description = "pop -> Can pop from singleton list"
+
+[6dcbb2c9-d98a-47bc-a010-9c19703d3ea2]
+description = "pop -> Can pop from non-empty list"
+
+[e83aade9-f030-4096-aaf0-f9dc6491e6cf]
+description = "pop -> Can pop multiple items"
+
+[5c46bcf2-c0a9-4654-ae17-f3192436fcf1]
+description = "pop -> Pop updates the count"
+
+[70d747a1-2e84-4ebc-bc3f-dcbee6a05f6b]
+description = "push -> Can push to an empty list"
+include = false
+
+[f3197f0a-1fea-45a5-939f-4a5ea60387ec]
+description = "push -> Can push to an empty list"
+reimplements = "70d747a1-2e84-4ebc-bc3f-dcbee6a05f6b"
+
+[391e332e-1f91-4033-b1e0-0e0c17812fa7]
+description = "push -> Can push to a non-empty list"
+
+[ed4b0e01-3bbd-4895-af25-152b5914b3da]
+description = "push -> Push updates count"
+
+[41666790-b932-4e5a-b323-e848a83d12d5]
+description = "push -> Push and pop"
+
+[930a4a5c-76f6-47ec-9be3-4e70993173a1]
+description = "peek -> Peek on empty list is an error"
+
+[43255a50-d919-4e81-afce-e4a271eaedbd]
+description = "peek -> Can peek on singleton list"
+
+[48353020-e25d-4621-a854-e35fb1e15fa7]
+description = "peek -> Can peek on non-empty list"
+
+[96fcead9-a713-46c2-8005-3f246c873851]
+description = "peek -> Peek does not change the count"
+
+[7576ed05-7ff7-4b84-8efb-d34d62c110f5]
+description = "peek -> Can peek after a pop and push"
+
+[b97d00b6-2fab-435d-ae74-3233dcc13698]
+description = "toList LIFO -> Empty linked list to list is empty"
+include = false
+comment = "Implements FIFO"
+
+[eedeb95f-b5cf-431d-8ad6-5854ba6b251c]
+description = "toList LIFO -> To list with multiple values"
+include = false
+comment = "Implements FIFO"
+
+[838678de-eaf3-4c14-b34e-7e35b6d851e8]
+description = "toList LIFO -> To list after a pop"
+include = false
+comment = "Implements FIFO"
+
+[03fc83a5-48a8-470b-a2d2-a286c5e8365f]
+description = "toList FIFO -> Empty linked list to list is empty"
+
+[1282484e-a58c-426a-972e-90746bda61fc]
+description = "toList FIFO -> To list with multiple values"
+
+[05ca3109-1249-4c0c-a567-a3b2f8352a7c]
+description = "toList FIFO -> To list after a pop"
+
+[5e6c1a3d-e34b-46d3-be59-3f132a820ed5]
+description = "reverse -> Reversed empty list has same values"
+
+[93c87ed3-862a-474f-820b-ba3fd6b6daf6]
+description = "reverse -> Reversed singleton list is same list"
+
+[92851ebe-9f52-4406-b92e-0718c441a2ab]
+description = "reverse -> Reversed non-empty list is reversed"
+include = false
+
+[1210eeda-b23f-4790-930c-7ac6d0c8e723]
+description = "reverse -> Reversed non-empty list is reversed"
+reimplements = "92851ebe-9f52-4406-b92e-0718c441a2ab"
+
+[9b53af96-7494-4cfa-9b77-b7366fed5c4c]
+description = "reverse -> Double reverse"