Add practice exercise piecing-it-together

config.json

@@ -2675,6 +2675,25 @@
         ],
         "difficulty": 7
       },
+      {
+        "slug": "piecing-it-together",
+        "name": "Piecing It Together",
+        "uuid": "e20ce41a-ff3f-46e4-9fbb-8810883c488f",
+        "practices": [
+          "structs"
+        ],
+        "prerequisites": [
+          "structs",
+          "errors",
+          "multiple-clause-functions",
+          "pattern-matching",
+          "guards",
+          "if",
+          "case",
+          "floating-point-numbers"
+        ],
+        "difficulty": 7
+      },
       {
         "slug": "queen-attack",
         "name": "Queen Attack",

exercises/practice/piecing-it-together/.docs/instructions.md

@@ -0,0 +1,41 @@
+# Instructions
+
+Given partial information about a jigsaw puzzle, add the missing pieces.
+
+If the information is insufficient to complete the details, or if given parts are in contradiction, the user should be notified.
+
+The full information about the jigsaw puzzle contains the following parts:
+
+- `pieces`: Total number of pieces
+- `border`: Number of border pieces
+- `inside`: Number of inside (non-border) pieces
+- `rows`: Number of rows
+- `columns`: Number of columns
+- `aspectRatio`: Aspect ratio of columns to rows
+- `format`: Puzzle format, which can be `portrait`, `square`, or `landscape`
+
+For this exercise, you may assume square pieces, so that the format can be derived from the aspect ratio:
+
+- If the aspect ratio is less than 1, it's `portrait`
+- If it is equal to 1, it's `square`
+- If it is greater than 1, it's `landscape`
+
+## Three examples
+
+### Portrait
+
+A portrait jigsaw puzzle with 6 pieces, all of which are border pieces and none are inside pieces. It has 3 rows and 2 columns. The aspect ratio is 1.5 (3/2).
+
+![A 2 by 3 jigsaw puzzle](https://assets.exercism.org/images/exercises/piecing-it-together/jigsaw-puzzle-2x3.svg)
+
+### Square
+
+A square jigsaw puzzle with 9 pieces, all of which are border pieces except for the one in the center, which is an inside piece. It has 3 rows and 3 columns. The aspect ratio is 1 (3/3).
+
+![A 3 by 3 jigsaw puzzle](https://assets.exercism.org/images/exercises/piecing-it-together/jigsaw-puzzle-3x3.svg)
+
+### Landscape
+
+A landscape jigsaw puzzle with 12 pieces, 10 of which are border pieces and 2 are inside pieces. It has 3 rows and 4 columns. The aspect ratio is 1.333333... (4/3).
+
+![A 4 by 3 jigsaw puzzle](https://assets.exercism.org/images/exercises/piecing-it-together/jigsaw-puzzle-4x3.svg)

exercises/practice/piecing-it-together/.docs/introduction.md

@@ -0,0 +1,6 @@
+# Introduction
+
+Your best friend has started collecting jigsaw puzzles and wants to build a detailed catalog of their collection — recording information such as the total number of pieces, the number of rows and columns, the number of border and inside pieces, aspect ratio, and puzzle format.
+Even with your powers combined, it takes multiple hours to solve a single jigsaw puzzle with one thousand pieces — and then you still need to count the rows and columns and calculate the remaining numbers manually.
+The even larger puzzles with thousands of pieces look quite daunting now.
+"There has to be a better way!" you exclaim and sit down in front of your computer to solve the problem.

exercises/practice/piecing-it-together/.formatter.exs

@@ -0,0 +1,4 @@
+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

exercises/practice/piecing-it-together/.gitignore

@@ -0,0 +1,26 @@
+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Ignore .fetch files in case you like to edit your project deps locally.
+/.fetch
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+piecing_it_together-*.tar
+
+# Temporary files, for example, from tests.
+/tmp/

exercises/practice/piecing-it-together/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "jiegillet"
+  ],
+  "files": {
+    "solution": [
+      "lib/piecing_it_together.ex"
+    ],
+    "test": [
+      "test/piecing_it_together_test.exs"
+    ],
+    "example": [
+      ".meta/example.ex"
+    ]
+  },
+  "blurb": "Fill in missing jigsaw puzzle details from partial data",
+  "source": "atk just started another 1000-pieces jigsaw puzzle when this idea hit him",
+  "source_url": "https://github.com/exercism/problem-specifications/pull/2554"
+}

exercises/practice/piecing-it-together/.meta/example.ex

@@ -0,0 +1,174 @@
+defmodule PiecingItTogether do
+  @doc """
+  TODO: add function description and replace types in @spec
+  """
+
+  defmodule JigsawPuzzle do
+    @type format() :: :landscape | :portrait | :square
+    @type t() :: %__MODULE__{
+            pieces: pos_integer(),
+            rows: pos_integer(),
+            columns: pos_integer(),
+            format: format(),
+            aspect_ratio: float(),
+            border: pos_integer(),
+            inside: pos_integer()
+          }
+
+    defstruct [:pieces, :rows, :columns, :format, :aspect_ratio, :border, :inside]
+  end
+
+  @spec jigsaw_data(jigsaw_puzzle :: JigsawPuzzle.t()) ::
+          {:ok, JigsawPuzzle.t()} | {:error, String.t()}
+  def jigsaw_data(%JigsawPuzzle{} = jigsaw_puzzle) do
+    jigsaw_puzzle
+    |> Map.from_struct()
+    |> Enum.filter(fn {_, value} -> value end)
+    |> Enum.sort_by(fn {key, _} -> key end)
+    |> complete_jigsaw_data()
+  end
+
+  defp complete_jigsaw_data(aspect_ratio: aspect_ratio, pieces: pieces) do
+    columns = round(:math.sqrt(aspect_ratio * pieces))
+    rows = Integer.floor_div(pieces, columns)
+    border = 2 * (rows + columns) - 4
+    inside = pieces - border
+
+    {:ok,
+     %JigsawPuzzle{
+       pieces: pieces,
+       rows: rows,
+       columns: columns,
+       format: aspect_ratio_to_format(aspect_ratio),
+       aspect_ratio: aspect_ratio,
+       border: border,
+       inside: inside
+     }}
+  end
+
+  defp complete_jigsaw_data(format: :square, rows: rows) do
+    columns = rows
+    pieces = rows * columns
+    border = 2 * (rows + columns) - 4
+    inside = pieces - border
+
+    {:ok,
+     %JigsawPuzzle{
+       pieces: pieces,
+       rows: rows,
+       columns: columns,
+       format: :square,
+       aspect_ratio: 1.0,
+       border: border,
+       inside: inside
+     }}
+  end
+
+  defp complete_jigsaw_data(format: _, rows: _) do
+    {:error, "Insufficient data"}
+  end
+
+  defp complete_jigsaw_data(aspect_ratio: 1.0, inside: inside) do
+    columns = 2 + round(:math.sqrt(inside))
+    rows = columns
+    pieces = rows * columns
+    border = pieces - inside
+
+    {:ok,
+     %JigsawPuzzle{
+       pieces: pieces,
+       rows: rows,
+       columns: columns,
+       format: :square,
+       aspect_ratio: 1.0,
+       border: border,
+       inside: inside
+     }}
+  end
+
+  defp complete_jigsaw_data(aspect_ratio: _, inside: _) do
+    {:error, "Insufficient data"}
+  end
+
+  defp complete_jigsaw_data(aspect_ratio: aspect_ratio, rows: rows) do
+    columns = round(rows * aspect_ratio)
+    pieces = rows * columns
+    border = 2 * (rows + columns) - 4
+    inside = pieces - border
+
+    {:ok,
+     %JigsawPuzzle{
+       pieces: pieces,
+       rows: rows,
+       columns: columns,
+       format: aspect_ratio_to_format(aspect_ratio),
+       aspect_ratio: aspect_ratio,
+       border: border,
+       inside: inside
+     }}
+  end
+
+  defp complete_jigsaw_data(border: border, format: :square, pieces: pieces) do
+    complete_jigsaw_data(aspect_ratio: 1.0, inside: pieces - border)
+  end
+
+  defp complete_jigsaw_data(border: border, format: format, pieces: pieces) do
+    center = 1 + border / 4
+    diff = :math.sqrt(center ** 2 - pieces)
+
+    {rows, columns} =
+      case format do
+        :landscape -> {round(center - diff), round(center + diff)}
+        :portrait -> {round(center + diff), round(center - diff)}
+      end
+
+    aspect_ratio = columns / rows
+    inside = pieces - border
+
+    {:ok,
+     %JigsawPuzzle{
+       pieces: pieces,
+       rows: rows,
+       columns: columns,
+       format: format,
+       aspect_ratio: aspect_ratio,
+       border: border,
+       inside: inside
+     }}
+  end
+
+  defp complete_jigsaw_data(columns: columns, format: format, rows: rows) do
+    aspect_ratio = columns / rows
+
+    if format == aspect_ratio_to_format(aspect_ratio) do
+      pieces = rows * columns
+      border = 2 * (rows + columns) - 4
+      inside = rows * columns - border
+
+      {:ok,
+       %JigsawPuzzle{
+         pieces: pieces,
+         rows: rows,
+         columns: columns,
+         format: format,
+         aspect_ratio: aspect_ratio,
+         border: border,
+         inside: inside
+       }}
+    else
+      {:error, "Contradictory data"}
+    end
+  end
+
+  defp complete_jigsaw_data(_) do
+    {:error, "Insufficient data"}
+  end
+
+  defp aspect_ratio_to_format(aspect_ratio) do
+    case aspect_ratio do
+      aspect_ratio when aspect_ratio < 1 -> :portrait
+      aspect_ratio when aspect_ratio > 1 -> :landscape
+      _ -> :square
+    end
+  end
+end

exercises/practice/piecing-it-together/.meta/tests.toml

@@ -0,0 +1,31 @@
+# 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.
+
+[ad626f23-09a2-4f5f-ba22-eec0671fa2a9]
+description = "1000 pieces puzzle with 1.6 aspect ratio"
+
+[3e0c5919-3561-42f5-b9ed-26d70c20214e]
+description = "square puzzle with 32 rows"
+
+[1126f160-b094-4dc2-bf37-13e36e394867]
+description = "400 pieces square puzzle with only inside pieces and aspect ratio"
+
+[a9743178-5642-4cc0-8fdb-00d6b031c3a0]
+description = "1500 pieces landscape puzzle with 30 rows and 1.6 aspect ratio"
+
+[f6378369-989c-497f-a6e2-f30b1fa76cba]
+description = "300 pieces portrait puzzle with 70 border pieces"
+
+[f53f82ba-5663-4c7e-9e86-57fdbb3e53d2]
+description = "puzzle with insufficient data"
+
+[a3d5c31a-cc74-44bf-b4fc-9e4d65f1ac1a]
+description = "puzzle with contradictory data"

exercises/practice/piecing-it-together/lib/piecing_it_together.ex

@@ -0,0 +1,25 @@
+defmodule PiecingItTogether do
+  @doc """
+  Fill in missing jigsaw puzzle details from partial data
+  """
+
+  defmodule JigsawPuzzle do
+    @type format() :: :landscape | :portrait | :square
+    @type t() :: %__MODULE__{
+            pieces: pos_integer(),
+            rows: pos_integer(),
+            columns: pos_integer(),
+            format: format(),
+            aspect_ratio: float(),
+            border: pos_integer(),
+            inside: pos_integer()
+          }
+
+    defstruct [:pieces, :rows, :columns, :format, :aspect_ratio, :border, :inside]
+  end
+
+  @spec jigsaw_data(jigsaw_puzzle :: JigsawPuzzle.t()) ::
+          {:ok, JigsawPuzzle.t()} | {:error, String.t()}
+  def jigsaw_data(jigsaw_puzzle) do
+  end
+end

exercises/practice/piecing-it-together/mix.exs

@@ -0,0 +1,27 @@
+defmodule PiecingItTogether.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :piecing_it_together,
+      version: "0.1.0",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      # {:dep_from_hexpm, "~> 0.3.0"},
+      # {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"}
+    ]
+  end
+end