Add spiral matrix exercise

config.json

@@ -561,6 +561,14 @@
         ],
         "difficulty": 5
       },
+      {
+        "slug": "spiral-matrix",
+        "name": "Spiral Matrix",
+        "uuid": "44f6c85e-a99c-4bf1-9269-67d9f25e93df",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 5
+      },
       {
         "slug": "sum-of-multiples",
         "name": "Sum of Multiples",

exercises/practice/spiral-matrix/.docs/instructions.md

@@ -0,0 +1,24 @@
+# Instructions
+
+Given the size, return a square matrix of numbers in spiral order.
+
+The matrix should be filled with natural numbers, starting from 1 in the top-left corner, increasing in an inward, clockwise spiral order.
+
+## Examples
+
+### Spiral matrix of size 3
+
+```text
+1 2 3
+8 9 4
+7 6 5
+```
+
+### Spiral matrix of size 4
+
+```text
+ 1  2  3 4
+12 13 14 5
+11 16 15 6
+10  9  8 7
+```

exercises/practice/spiral-matrix/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "mr-sigma"
+  ],
+  "files": {
+    "solution": [
+      "spiral_matrix.rb"
+    ],
+    "test": [
+      "spiral_matrix_test.rb"
+    ],
+    "example": [
+      ".meta/example.rb"
+    ]
+  },
+  "blurb": "Given the size, return a square matrix of numbers in spiral order.",
+  "source": "Reddit r/dailyprogrammer challenge #320 [Easy] Spiral Ascension.",
+  "source_url": "https://web.archive.org/web/20230607064729/https://old.reddit.com/r/dailyprogrammer/comments/6i60lr/20170619_challenge_320_easy_spiral_ascension/"
+}

exercises/practice/spiral-matrix/.meta/example.rb

@@ -0,0 +1,48 @@
+class SpiralMatrix
+  private
+  attr_reader :counter, :dx, :dy, :x, :y
+
+  def initialize_matrix
+    Array.new(size) { Array.new(size, 0) }
+  end
+
+  def generate_matrix
+    while matrix_includes_zeroes?
+      @matrix[y][x] = counter
+
+      @dy, @dx = @dx, -@dy if next_step_invalid?
+
+      @x += dx
+      @y += dy
+
+      @counter += 1
+    end
+  end
+
+  def next_step_invalid?
+    @y + @dy == @size ||
+      (@y + @dy).negative? ||
+      @x + @dx == @size ||
+      (@x + @dx).negative? ||
+      (@matrix[@y + @dy][@x + @dx]).positive?
+  end
+
+  def matrix_includes_zeroes?
+    @matrix.any? { |row| row.any?(0) }
+  end
+
+  public
+  attr_reader :size, :matrix
+
+  def initialize(size)
+    @size = size
+    @matrix = initialize_matrix
+    @dx = 1
+    @dy = 0
+    @y = 0
+    @x = 0
+    @counter = 1
+
+    generate_matrix
+  end
+end

exercises/practice/spiral-matrix/.meta/tests.toml

@@ -0,0 +1,28 @@
+# 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.
+
+[8f584201-b446-4bc9-b132-811c8edd9040]
+description = "empty spiral"
+
+[e40ae5f3-e2c9-4639-8116-8a119d632ab2]
+description = "trivial spiral"
+
+[cf05e42d-eb78-4098-a36e-cdaf0991bc48]
+description = "spiral of size 2"
+
+[1c475667-c896-4c23-82e2-e033929de939]
+description = "spiral of size 3"
+
+[05ccbc48-d891-44f5-9137-f4ce462a759d]
+description = "spiral of size 4"
+
+[f4d2165b-1738-4e0c-bed0-c459045ae50d]
+description = "spiral of size 5"

exercises/practice/spiral-matrix/spiral_matrix.rb

@@ -0,0 +1,7 @@
+=begin
+Write your code for the 'Spiral Matrix' exercise in this file. Make the tests in
+`spiraL_matrix_test.rb` pass.
+
+To get started with TDD, see the `README.md` file in your
+`ruby/spiral-matrix` directory.
+=end

exercises/practice/spiral-matrix/spiral_matrix_test.rb

@@ -0,0 +1,64 @@
+require 'minitest/autorun'
+require_relative 'spiral_matrix'
+
+class SpiralMatrixTest < Minitest::Test
+  def test_empty_spiral
+    # skip
+    spiral = SpiralMatrix.new(0).matrix
+    expected = []
+    assert_equal expected, spiral
+  end
+
+  def test_trivial_spiral
+    skip
+    spiral = SpiralMatrix.new(1).matrix
+    expected = [[1]]
+    assert_equal expected, spiral
+  end
+
+  def test_spiral_of_size_2
+    skip
+    spiral = SpiralMatrix.new(2).matrix
+    expected = [
+      [1, 2],
+      [4, 3]
+    ]
+    assert_equal expected, spiral
+  end
+
+  def test_spiral_of_size_3
+    skip
+    spiral = SpiralMatrix.new(3).matrix
+    expected = [
+      [1, 2, 3],
+      [8, 9, 4],
+      [7, 6, 5]
+    ]
+    assert_equal expected, spiral
+  end
+
+  def test_spiral_of_size_4
+    skip
+    spiral = SpiralMatrix.new(4).matrix
+    expected = [
+      [1, 2, 3, 4],
+      [12, 13, 14, 5],
+      [11, 16, 15, 6],
+      [10, 9, 8, 7]
+    ]
+    assert_equal expected, spiral
+  end
+
+  def test_spiral_of_size_5
+    skip
+    spiral = SpiralMatrix.new(5).matrix
+    expected = [
+      [1, 2, 3, 4, 5],
+      [16, 17, 18, 19, 6],
+      [15, 24, 25, 20, 7],
+      [14, 23, 22, 21, 8],
+      [13, 12, 11, 10, 9]
+    ]
+    assert_equal expected, spiral
+  end
+end