Add dominoes exercise

config.json

@@ -743,6 +743,14 @@
         "prerequisites": [],
         "difficulty": 7
       },
+      {
+        "slug": "dominoes",
+        "name": "Dominoes",
+        "uuid": "62072c25-d963-467a-8bea-36b209a861e6",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 7
+      },
       {
         "slug": "word-search",
         "name": "Word Search",

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

@@ -0,0 +1,13 @@
+# Instructions
+
+Make a chain of dominoes.
+
+Compute a way to order a given set of dominoes in such a way that they form a correct domino chain (the dots on one half of a stone match the dots on the neighboring half of an adjacent stone) and that dots on the halves of the stones which don't have a neighbor (the first and last stone) 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/.meta/config.json

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

exercises/practice/dominoes/.meta/example.v

@@ -0,0 +1,38 @@
+module main
+
+type Domino = []int
+
+fn search(mut dominoes []Domino, remaining int) bool {
+    if remaining == 0 {
+        return dominoes[0][0] == dominoes[dominoes.len - 1][1]
+    }
+
+    for i in 0..remaining {
+        if dominoes[i][0] == dominoes[remaining][0] {
+            dominoes[i][0], dominoes[i][1] = dominoes[i][1], dominoes[i][0]
+        }
+
+        if dominoes[i][1] != dominoes[remaining][0] {
+            continue
+        }
+
+        dominoes[i], dominoes[remaining - 1] = dominoes[remaining - 1], dominoes[i]
+
+        if search(mut dominoes, remaining - 1) {
+            return true
+        }
+
+        dominoes[i], dominoes[remaining - 1] = dominoes[remaining - 1], dominoes[i]
+    }
+
+    return false
+}
+
+fn can_chain(dominoes []Domino) bool {
+    if dominoes.len == 0 {
+        return true
+    }
+
+    mut dominoes2 := dominoes.clone()
+    return search(mut dominoes2, dominoes.len - 1)
+}

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

@@ -0,0 +1,42 @@
+# This is an auto-generated file. Regular comments will be removed when this
+# file is regenerated. Regenerating will not touch any manually added keys,
+# so comments can be added in 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.v

@@ -0,0 +1,6 @@
+module main
+
+type Domino = []int
+
+fn can_chain(dominoes []Domino) bool {
+}

exercises/practice/dominoes/run_test.v

@@ -0,0 +1,66 @@
+module main
+
+fn test_empty_input_empty_output() {
+	dominoes := [][]int{}
+	assert can_chain(dominoes)
+}
+
+fn test_singleton_input_singleton_output() {
+	dominoes := [[1, 1]]
+	assert can_chain(dominoes)
+}
+
+fn test_singleton_that_cant_be_chained() {
+	dominoes := [[1, 2]]
+	assert !can_chain(dominoes)
+}
+
+fn test_three_elements() {
+	dominoes := [[1, 2], [3, 1], [2, 3]]
+	assert can_chain(dominoes)
+}
+
+fn test_can_reverse_dominoes() {
+	dominoes := [[1, 2], [1, 3], [2, 3]]
+	assert can_chain(dominoes)
+}
+
+fn test_cant_be_chained() {
+	dominoes := [[1, 2], [4, 1], [2, 3]]
+	assert !can_chain(dominoes)
+}
+
+fn test_disconnected___simple() {
+	dominoes := [[1, 1], [2, 2]]
+	assert !can_chain(dominoes)
+}
+
+fn test_disconnected___double_loop() {
+	dominoes := [[1, 2], [2, 1], [3, 4], [4, 3]]
+	assert !can_chain(dominoes)
+}
+
+fn test_disconnected___single_isolated() {
+	dominoes := [[1, 2], [2, 3], [3, 1], [4, 4]]
+	assert !can_chain(dominoes)
+}
+
+fn test_need_backtrack() {
+	dominoes := [[1, 2], [2, 3], [3, 1], [2, 4], [2, 4]]
+	assert can_chain(dominoes)
+}
+
+fn test_separate_loops() {
+	dominoes := [[1, 2], [2, 3], [3, 1], [1, 1], [2, 2], [3, 3]]
+	assert can_chain(dominoes)
+}
+
+fn test_nine_elements() {
+	dominoes := [[1, 2], [5, 3], [3, 1], [1, 2], [2, 4], [1, 6], [2, 3], [3, 4], [5, 6]]
+	assert can_chain(dominoes)
+}
+
+fn test_separate_three_domino_loops() {
+	dominoes := [[1, 2], [2, 3], [3, 1], [4, 5], [5, 6], [6, 4]]
+	assert !can_chain(dominoes)
+}