Add dominoes (#488)

Author: keiravillekode

config.json

@@ -947,6 +947,14 @@
         "prerequisites": [],
         "difficulty": 6
       },
+      {
+        "slug": "dominoes",
+        "name": "Dominoes",
+        "uuid": "9260be95-c9a5-4975-a00e-21828f5e9241",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 7
+      },
       {
         "slug": "knapsack",
         "name": "Knapsack",

exercises/practice/dominoes/.docs/instructions.append.md

@@ -0,0 +1,3 @@
+# Instructions Append
+
+Each stone is represented as a dotted pair.

exercises/practice/dominoes/.docs/instructions.md

@@ -0,0 +1,15 @@
+# Instructions
+
+Make a chain of dominoes.
+
+Compute a way to order a given set of domino stones so that they form a correct domino chain.
+In the chain, the dots on one half of a stone must match the dots on the neighboring half of an adjacent stone.
+Additionally, the dots on the halves of the stones without neighbors (the first and last stone) must match each other.
+
+For example given the stones `[2|1]`, `[2|3]` and `[1|3]` you should compute something
+like `[1|2] [2|3] [3|1]` or `[3|2] [2|1] [1|3]` or `[1|3] [3|2] [2|1]` etc, where the first and last numbers are the same.
+
+For stones `[1|2]`, `[4|1]` and `[2|3]` the resulting chain is not valid: `[4|1] [1|2] [2|3]`'s first and last numbers are not the same.
+4 != 3
+
+Some test cases may use duplicate stones in a chain solution, assume that multiple Domino sets are being used.

exercises/practice/dominoes/.docs/introduction.md

@@ -0,0 +1,13 @@
+# Introduction
+
+In Toyland, the trains are always busy delivering treasures across the city, from shiny marbles to rare building blocks.
+The tracks they run on are made of colorful domino-shaped pieces, each marked with two numbers.
+For the trains to move, the dominoes must form a perfect chain where the numbers match.
+
+Today, an urgent delivery of rare toys is on hold.
+You've been handed a set of track pieces to inspect.
+If they can form a continuous chain, the train will be on its way, bringing smiles across Toyland.
+If not, the set will be discarded, and another will be tried.
+
+The toys are counting on you to solve this puzzle.
+Will the dominoes connect the tracks and send the train rolling, or will the set be left behind?

exercises/practice/dominoes/.meta/config.json

@@ -0,0 +1,17 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "dominoes.el"
+    ],
+    "test": [
+      "dominoes-test.el"
+    ],
+    "example": [
+      ".meta/example.el"
+    ]
+  },
+  "blurb": "Make a chain of dominoes."
+}

exercises/practice/dominoes/.meta/example.el

@@ -0,0 +1,34 @@
+;;; dominoes.el --- Dominoes (exercism)  -*- lexical-binding: t; -*-
+
+;;; Commentary:
+
+;;; Code:
+
+(require 'cl-lib)
+(require 'seq)
+
+(defun evenp (number)
+  (= (logand number 1) 0))
+
+(defun can-chain (dominoes)
+  (letrec ((table-length 7)
+           (numbers (cl-loop for i below table-length collect i))
+           (tally (make-vector table-length 0))
+           (parent (vconcat numbers))
+           (root (lambda (number)
+                   (if (= (aref parent number) number)
+                     number
+                     (funcall root (aref parent number)))))
+           (process (lambda (stone)
+             (aset tally (car stone) (1+ (aref tally (car stone))))
+             (aset tally (cdr stone) (1+ (aref tally (cdr stone))))
+             (aset parent (funcall root (cdr stone)) (funcall root (car stone)))))
+           (rootp (lambda (number)
+                    (and (> (aref tally number) 0) (= (funcall root number) number)))))
+    (mapc process dominoes)
+    (and (seq-every-p #'evenp tally) (length< (seq-filter rootp numbers) 2))))
+
+
+(provide 'dominoes)
+;;; dominoes.el ends here
+

exercises/practice/dominoes/.meta/tests.toml

@@ -0,0 +1,49 @@
+# 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.
+
+[31a673f2-5e54-49fe-bd79-1c1dae476c9c]
+description = "empty input = empty output"
+
+[4f99b933-367b-404b-8c6d-36d5923ee476]
+description = "singleton input = singleton output"
+
+[91122d10-5ec7-47cb-b759-033756375869]
+description = "singleton that can't be chained"
+
+[be8bc26b-fd3d-440b-8e9f-d698a0623be3]
+description = "three elements"
+
+[99e615c6-c059-401c-9e87-ad7af11fea5c]
+description = "can reverse dominoes"
+
+[51f0c291-5d43-40c5-b316-0429069528c9]
+description = "can't be chained"
+
+[9a75e078-a025-4c23-8c3a-238553657f39]
+description = "disconnected - simple"
+
+[0da0c7fe-d492-445d-b9ef-1f111f07a301]
+description = "disconnected - double loop"
+
+[b6087ff0-f555-4ea0-a71c-f9d707c5994a]
+description = "disconnected - single isolated"
+
+[2174fbdc-8b48-4bac-9914-8090d06ef978]
+description = "need backtrack"
+
+[167bb480-dfd1-4318-a20d-4f90adb4a09f]
+description = "separate loops"
+
+[cd061538-6046-45a7-ace9-6708fe8f6504]
+description = "nine elements"
+
+[44704c7c-3adb-4d98-bd30-f45527cf8b49]
+description = "separate three-domino loops"

exercises/practice/dominoes/dominoes-test.el

@@ -0,0 +1,65 @@
+;;; dominoes-test.el --- Tests for Dominoes (exercism)  -*- lexical-binding: t; -*-
+
+;;; Commentary:
+
+;;; Code:
+
+
+(load-file "dominoes.el")
+(declare-function can-chain "dominoes.el" (dominoes))
+
+
+(ert-deftest empty-input-=-empty-output ()
+  (should (can-chain [])))
+
+
+(ert-deftest singleton-input-=-singleton-output ()
+  (should (can-chain [(1 . 1)])))
+
+
+(ert-deftest singleton-that-cant-be-chained ()
+  (should-not (can-chain [(1 . 2)])))
+
+
+(ert-deftest three-elements ()
+  (should (can-chain [(1 . 2) (3 . 1) (2 . 3)])))
+
+
+(ert-deftest can-reverse-dominoes ()
+  (should (can-chain [(1 . 2) (1 . 3) (2 . 3)])))
+
+
+(ert-deftest cant-be-chained ()
+  (should-not (can-chain [(1 . 2) (4 . 1) (2 . 3)])))
+
+
+(ert-deftest disconnected---simple ()
+  (should-not (can-chain [(1 . 1) (2 . 2)])))
+
+
+(ert-deftest disconnected---double-loop ()
+  (should-not (can-chain [(1 . 2) (2 . 1) (3 . 4) (4 . 3)])))
+
+
+(ert-deftest disconnected---single-isolated ()
+  (should-not (can-chain [(1 . 2) (2 . 3) (3 . 1) (4 . 4)])))
+
+
+(ert-deftest need-backtrack ()
+  (should (can-chain [(1 . 2) (2 . 3) (3 . 1) (2 . 4) (2 . 4)])))
+
+
+(ert-deftest separate-loops ()
+  (should (can-chain [(1 . 2) (2 . 3) (3 . 1) (1 . 1) (2 . 2) (3 . 3)])))
+
+
+(ert-deftest nine-elements ()
+  (should (can-chain [(1 . 2) (5 . 3) (3 . 1) (1 . 2) (2 . 4) (1 . 6) (2 . 3) (3 . 4) (5 . 6)])))
+
+
+(ert-deftest separate-three-domino-loops ()
+  (should-not (can-chain [(1 . 2) (2 . 3) (3 . 1) (4 . 5) (5 . 6) (6 . 4)])))
+
+
+(provide 'dominoes-test)
+;;; dominoes-test.el ends here

exercises/practice/dominoes/dominoes.el

@@ -0,0 +1,14 @@
+;;; dominoes.el --- Dominoes (exercism)  -*- lexical-binding: t; -*-
+
+;;; Commentary:
+
+;;; Code:
+
+
+(defun can-chain (dominoes)
+  (error "Delete this S-Expression and write your own implementation"))
+
+
+(provide 'dominoes)
+;;; dominoes.el ends here
+