Add game-of-life exercise (#347)

* Add `game-of-life` exercise

* Minor fixes

* Fix import

* Install dplyr in CI

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
 
     steps:
       - uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332
-      
+
       - uses: r-lib/actions/setup-r@v2
         with:
           r-version: 4.3.1
@@ -40,18 +40,18 @@ jobs:
 
     strategy:
       matrix:
-        R: [ '4.3.1' ]
+        R: ["4.3.1"]
 
     steps:
       - uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332
-      
+
       - uses: r-lib/actions/setup-r@v2
         with:
           r-version: ${{ matrix.R }}
 
       - name: Install project dependencies
         run: |
-          install.packages(c("testthat", "jsonlite", "lintr"))
+          install.packages(c("testthat", "jsonlite", "lintr", "dplyr"))
         shell: Rscript {0}
 
       - name: Run exercism/r ci (runs tests) for all exercises

config.json

@@ -656,6 +656,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 3
+      },
+      {
+        "slug": "game-of-life",
+        "name": "Conway's Game of Life",
+        "uuid": "5ba723f2-dd9e-452a-b5f3-cfe19a2650b5",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 4
       }
     ]
   },

exercises/practice/game-of-life/.docs/instructions.md

@@ -0,0 +1,11 @@
+# Instructions
+
+After each generation, the cells interact with their eight neighbors, which are cells adjacent horizontally, vertically, or diagonally.
+
+The following rules are applied to each cell:
+
+- Any live cell with two or three live neighbors lives on.
+- Any dead cell with exactly three live neighbors becomes a live cell.
+- All other cells die or stay dead.
+
+Given a matrix of 1s and 0s (corresponding to live and dead cells), apply the rules to each cell, and return the next generation.

exercises/practice/game-of-life/.docs/introduction.md

@@ -0,0 +1,9 @@
+# Introduction
+
+[Conway's Game of Life][game-of-life] is a fascinating cellular automaton created by the British mathematician John Horton Conway in 1970.
+
+The game consists of a two-dimensional grid of cells that can either be "alive" or "dead."
+
+After each generation, the cells interact with their eight neighbors via a set of rules, which define the new generation.
+
+[game-of-life]: https://en.wikipedia.org/wiki/Conway%27s_Game_of_Life

exercises/practice/game-of-life/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "erikschierboom"
+  ],
+  "files": {
+    "solution": [
+      "game-of-life.R"
+    ],
+    "test": [
+      "test_game-of-life.R"
+    ],
+    "example": [
+      ".meta/example.R"
+    ]
+  },
+  "blurb": "Implement Conway's Game of Life.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Conway%27s_Game_of_Life"
+}

exercises/practice/game-of-life/.meta/example.R

@@ -0,0 +1,19 @@
+library(dplyr)
+
+tick <- function(cells) {
+  coords <- expand.grid(seq_len(nrow(cells)), seq_len(ncol(cells)))
+
+  matrix(apply(coords, 1, function(coord) {
+    cell <- cells[coord[1], coord[2]]
+    neighbor_coords <- dplyr::inner_join(
+      expand.grid(coord[1] + -1:1, coord[2] + -1:1),
+      coords
+    )
+    live_neighbors <- sum(
+      apply(neighbor_coords, 1, function (neighbor_coord) {
+        cells[neighbor_coord[1], neighbor_coord[2]]
+      })) - cell
+    ifelse(live_neighbors == 3 ||
+             live_neighbors == 2 && cell == 1, 1, 0)
+  }), nrow(cells))
+}

exercises/practice/game-of-life/.meta/tests.toml

@@ -0,0 +1,35 @@
+# 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.
+
+[ae86ea7d-bd07-4357-90b3-ac7d256bd5c5]
+description = "empty matrix"
+include = false
+
+[4ea5ccb7-7b73-4281-954a-bed1b0f139a5]
+description = "live cells with zero live neighbors die"
+
+[df245adc-14ff-4f9c-b2ae-f465ef5321b2]
+description = "live cells with only one live neighbor die"
+
+[2a713b56-283c-48c8-adae-1d21306c80ae]
+description = "live cells with two live neighbors stay alive"
+
+[86d5c5a5-ab7b-41a1-8907-c9b3fc5e9dae]
+description = "live cells with three live neighbors stay alive"
+
+[015f60ac-39d8-4c6c-8328-57f334fc9f89]
+description = "dead cells with three live neighbors become alive"
+
+[2ee69c00-9d41-4b8b-89da-5832e735ccf1]
+description = "live cells with four or more neighbors die"
+
+[a79b42be-ed6c-4e27-9206-43da08697ef6]
+description = "bigger matrix"

exercises/practice/game-of-life/game-of-life.R

@@ -0,0 +1,3 @@
+tick <- function(cells) {
+
+}

exercises/practice/game-of-life/test_game-of-life.R

@@ -0,0 +1,110 @@
+source("./game-of-life.R")
+library(testthat)
+
+test_that("live cells with zero live neighbors die", {
+  expect_equal(
+    tick(
+      matrix(
+        c(0, 0, 0,
+          0, 1, 0,
+          0, 0, 0), 3, byrow = TRUE)),
+    matrix(
+      c(0, 0, 0,
+        0, 0, 0,
+        0, 0, 0), 3, byrow = TRUE)
+  )
+})
+
+test_that("live cells with only one live neighbor die", {
+  expect_equal(
+    tick(
+      matrix(
+        c(0, 0, 0,
+          0, 1, 0,
+          0, 1, 0), 3, byrow = TRUE)),
+    matrix(
+      c(0, 0, 0,
+        0, 0, 0,
+        0, 0, 0), 3, byrow = TRUE)
+  )
+})
+
+test_that("live cells with two live neighbors stay alive", {
+  expect_equal(
+    tick(
+      matrix(
+        c(1, 0, 1,
+          1, 0, 1,
+          1, 0, 1), 3, byrow = TRUE)),
+    matrix(
+      c(0, 0, 0,
+        1, 0, 1,
+        0, 0, 0), 3, byrow = TRUE)
+    )
+})
+
+test_that("live cells with three live neighbors stay alive", {
+  expect_equal(
+    tick(
+      matrix(
+        c(0, 1, 0, 
+          1, 0, 0, 
+          1, 1, 0), 3, byrow = TRUE)),
+    matrix(
+      c(0, 0, 0, 
+        1, 0, 0, 
+        1, 1, 0), 3, byrow = TRUE)
+  )
+})
+
+test_that("dead cells with three live neighbors become alive", {
+  expect_equal(
+    tick(
+      matrix(
+        c(1, 1, 0, 
+          0, 0, 0, 
+          1, 0, 0), 3, byrow = TRUE)),
+    matrix(
+      c(0, 0, 0,
+        1, 1, 0,
+        0, 0, 0), 3, byrow = TRUE)
+  )
+})
+
+test_that("live cells with four or more neighbors die", {
+  expect_equal(
+    tick(
+      matrix(
+        c(1, 1, 1, 
+          1, 1, 1, 
+          1, 1, 1), 3, byrow = TRUE)),
+    matrix(
+      c(1, 0, 1, 
+        0, 0, 0, 
+        1, 0, 1), 3, byrow = TRUE)
+  )
+})
+
+test_that("bigger matrix", {
+  expect_equal(
+    tick(
+      matrix(
+        c(1, 1, 0, 1, 1, 0, 0, 0, 
+          1, 0, 1, 1, 0, 0, 0, 0, 
+          1, 1, 1, 0, 0, 1, 1, 1, 
+          0, 0, 0, 0, 0, 1, 1, 0, 
+          1, 0, 0, 0, 1, 1, 0, 0, 
+          1, 1, 0, 0, 0, 1, 1, 1, 
+          0, 0, 1, 0, 1, 0, 0, 1, 
+          1, 0, 0, 0, 0, 0, 1, 1), 8)),
+    matrix(
+      c(1, 1, 0, 1, 1, 0, 0, 0, 
+        0, 0, 0, 0, 0, 1, 1, 0, 
+        1, 0, 1, 1, 1, 1, 0, 1,
+        1, 0, 0, 0, 0, 0, 0, 1, 
+        1, 1, 0, 0, 1, 0, 0, 1, 
+        1, 1, 0, 1, 0, 0, 0, 1,
+        1, 0, 0, 0, 0, 0, 0, 0, 
+        0, 0, 0, 0, 0, 0, 1, 1), 8)
+  )
+})