[#793] New practice exercise word-search

config.json

@@ -2661,7 +2661,33 @@
           "bitstrings"
         ],
         "difficulty": 6
-      }
+       },
+       {
+        "slug": "word-search",
+        "name": "Word Search",
+        "uuid": "41ab29d0-e094-4910-bb51-b99bdedc7f17",
+        "prerequisites": [
+          "atoms",
+          "tuples",
+          "lists",
+          "enum",
+          "case",
+          "cond",
+          "if",
+          "multiple-clause-functions",
+          "pattern-matching",
+          "guards",
+          "strings",
+          "charlists",
+          "list-comprehensions",
+          "maps",
+          "structs"
+        ],
+        "practices": [
+          "list-comprehensions"
+        ],
+        "difficulty": 7
+       }
     ],
     "foregone": [
       "linked-list",

exercises/practice/word-search/.docs/instructions.md

@@ -0,0 +1,27 @@
+# Description
+
+In word search puzzles you get a square of letters and have to find specific
+words in them.
+
+For example:
+
+```text
+jefblpepre
+camdcimgtc
+oivokprjsm
+pbwasqroua
+rixilelhrs
+wolcqlirpc
+screeaumgr
+alxhpburyi
+jalaycalmp
+clojurermt
+```
+
+There are several programming languages hidden in the above square.
+
+Words can be hidden in all kinds of directions: left-to-right, right-to-left,
+vertical and diagonal.
+
+Given a puzzle and a list of words return the location of the first and last
+letter of each word.

exercises/practice/word-search/.formatter.exs

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

exercises/practice/word-search/.meta/config.json

@@ -0,0 +1,16 @@
+{
+  "authors": ["jiegillet"],
+  "contributors": [],
+  "files": {
+    "example": [
+      ".meta/example.ex"
+    ],
+    "solution": [
+      "lib/word_search.ex"
+    ],
+    "test": [
+      "test/word_search_test.exs"
+    ]
+  },
+  "blurb": "Create a program to solve a word search puzzle."
+}

exercises/practice/word-search/.meta/example.ex

@@ -0,0 +1,59 @@
+defmodule WordSearch do
+  defmodule Location do
+    defstruct [:from, :to]
+    @type t :: %Location{from: {integer, integer}, to: {integer, integer}}
+  end
+
+  @doc """
+  Find the start and end positions of words in a grid of letters.
+  Row and column positions are 1 indexed.
+  """
+  @spec search(grid :: String.t(), words :: [String.t()]) :: %{String.t() => nil | Location.t()}
+  def search(grid, words) do
+    grid =
+      String.split(grid, "\n")
+      |> Enum.map(&to_charlist/1)
+
+    {coord, starting_points} =
+      for {row, r} <- Enum.with_index(grid, 1),
+          {char, c} <- Enum.with_index(row, 1),
+          reduce: {%{}, %{}} do
+        {coord, starting_points} ->
+          {Map.put(coord, {r, c}, char),
+           Map.update(starting_points, char, [{r, c}], &[{r, c} | &1])}
+      end
+
+    Map.new(words, fn <<start, _::binary>> = word ->
+      {word, search(word, starting_points[start], coord)}
+    end)
+  end
+
+  def search(_word, nil, _coord), do: nil
+
+  def search(word, starting_points, coord) do
+    word_length = String.length(word)
+    word = to_charlist(word)
+
+    for point <- starting_points,
+        path <- make_paths(point, word_length - 1),
+        reduce: nil do
+      location ->
+        location ||
+          if word == Enum.map(path, &coord[&1]),
+            do: %Location{from: List.first(path), to: List.last(path)}
+    end
+  end
+
+  def make_paths({r, c}, delta) do
+    [
+      for(i <- 0..delta, do: {r + i, c}),
+      for(i <- 0..delta, do: {r - i, c}),
+      for(i <- 0..delta, do: {r, c + i}),
+      for(i <- 0..delta, do: {r, c - i}),
+      for(i <- 0..delta, do: {r + i, c + i}),
+      for(i <- 0..delta, do: {r + i, c - i}),
+      for(i <- 0..delta, do: {r - i, c + i}),
+      for(i <- 0..delta, do: {r - i, c - i})
+    ]
+  end
+end

exercises/practice/word-search/.meta/tests.toml

@@ -0,0 +1,69 @@
+# 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.
+[b4057815-0d01-41f0-9119-6a91f54b2a0a]
+description = "Should accept an initial game grid and a target search word"
+
+[6b22bcc5-6cbf-4674-931b-d2edbff73132]
+description = "Should locate one word written left to right"
+
+[ff462410-434b-442d-9bc3-3360c75f34a8]
+description = "Should locate the same word written left to right in a different position"
+
+[a02febae-6347-443e-b99c-ab0afb0b8fca]
+description = "Should locate a different left to right word"
+
+[e42e9987-6304-4e13-8232-fa07d5280130]
+description = "Should locate that different left to right word in a different position"
+
+[9bff3cee-49b9-4775-bdfb-d55b43a70b2f]
+description = "Should locate a left to right word in two line grid"
+
+[851a35fb-f499-4ec1-9581-395a87903a22]
+description = "Should locate a left to right word in three line grid"
+
+[2f3dcf84-ba7d-4b75-8b8d-a3672b32c035]
+description = "Should locate a left to right word in ten line grid"
+
+[006d4856-f365-4e84-a18c-7d129ce9eefb]
+description = "Should locate that left to right word in a different position in a ten line grid"
+
+[eff7ac9f-ff11-443e-9747-40850c12ab60]
+description = "Should locate a different left to right word in a ten line grid"
+
+[dea39f86-8c67-4164-8884-13bfc48bd13b]
+description = "Should locate multiple words"
+
+[29e6a6a5-f80c-48a6-8e68-05bbbe187a09]
+description = "Should locate a single word written right to left"
+
+[3cf34428-b43f-48b6-b332-ea0b8836011d]
+description = "Should locate multiple words written in different horizontal directions"
+
+[2c8cd344-a02f-464b-93b6-8bf1bd890003]
+description = "Should locate words written top to bottom"
+
+[9ee1e43d-e59d-4c32-9a5f-6a22d4a1550f]
+description = "Should locate words written bottom to top"
+
+[6a21a676-f59e-4238-8e88-9f81015afae9]
+description = "Should locate words written top left to bottom right"
+
+[c9125189-1861-4b0d-a14e-ba5dab29ca7c]
+description = "Should locate words written bottom right to top left"
+
+[b19e2149-7fc5-41ec-a8a9-9bc6c6c38c40]
+description = "Should locate words written bottom left to top right"
+
+[69e1d994-a6d7-4e24-9b5a-db76751c2ef8]
+description = "Should locate words written top right to bottom left"
+
+[695531db-69eb-463f-8bad-8de3bf5ef198]
+description = "Should fail to locate a word that is not in the puzzle"

exercises/practice/word-search/lib/word_search.ex

@@ -0,0 +1,14 @@
+defmodule WordSearch do
+  defmodule Location do
+    defstruct [:from, :to]
+    @type t :: %Location{from: {integer, integer}, to: {integer, integer}}
+  end
+
+  @doc """
+  Find the start and end positions of words in a grid of letters.
+  Row and column positions are 1 indexed.
+  """
+  @spec search(grid :: String.t(), words :: [String.t()]) :: %{String.t() => nil | Location.t()}
+  def search(grid, words) do
+  end
+end

exercises/practice/word-search/mix.exs

@@ -0,0 +1,28 @@
+defmodule WordSearch.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :word_search,
+      version: "0.1.0",
+      # elixir: "~> 1.8",
+      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

exercises/practice/word-search/test/test_helper.exs

@@ -0,0 +1,2 @@
+ExUnit.start()
+ExUnit.configure(exclude: :pending, trace: true)