Add go-counting exercise (#134)

config.json

@@ -583,6 +583,14 @@
         "prerequisites": [],
         "difficulty": 6
       },
+      {
+        "slug": "go-counting",
+        "name": "Go Counting",
+        "uuid": "8c81bf5c-5188-4e1b-9814-1f0f0fcdeec2",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 6
+      },
       {
         "slug": "gigasecond",
         "name": "Gigasecond",

exercises/practice/go-counting/.docs/instructions.md

@@ -0,0 +1,31 @@
+# Instructions
+
+Count the scored points on a Go board.
+
+In the game of go (also known as baduk, igo, cờ vây and wéiqí) points are gained by completely encircling empty intersections with your stones.
+The encircled intersections of a player are known as its territory.
+
+Calculate the territory of each player.
+You may assume that any stones that have been stranded in enemy territory have already been taken off the board.
+
+Determine the territory which includes a specified coordinate.
+
+Multiple empty intersections may be encircled at once and for encircling only horizontal and vertical neighbors count.
+In the following diagram the stones which matter are marked "O" and the stones that don't are marked "I" (ignored).
+Empty spaces represent empty intersections.
+
+```text
++----+
+|IOOI|
+|O  O|
+|O OI|
+|IOI |
++----+
+```
+
+To be more precise an empty intersection is part of a player's territory if all of its neighbors are either stones of that player or empty intersections that are part of that player's territory.
+
+For more information see [Wikipedia][go-wikipedia] or [Sensei's Library][go-sensei].
+
+[go-wikipedia]: https://en.wikipedia.org/wiki/Go_%28game%29
+[go-sensei]: https://senseis.xmp.net/

exercises/practice/go-counting/.meta/Example.roc

@@ -0,0 +1,128 @@
+module [territory, territories]
+
+Intersection : { x : U64, y : U64 }
+
+Stone : [White, Black, None]
+
+Territory : {
+    owner : Stone,
+    territory : Set Intersection,
+}
+
+Territories : {
+    black : Set Intersection,
+    white : Set Intersection,
+    none : Set Intersection,
+}
+
+Board : {
+    rows : List (List Stone),
+    width : U64,
+    height : U64,
+}
+
+parse : Str -> Result Board [BoardWasEmpty, BoardWasNotRectangular, InvalidChar U8]
+parse = \boardStr ->
+    if boardStr == "" then
+        Err BoardWasEmpty
+        else
+
+    rows =
+        boardStr
+            |> Str.split "\n"
+            |> List.mapTry? \row ->
+                row
+                |> Str.toUtf8
+                |> List.mapTry \char ->
+                    when char is
+                        'B' -> Ok Black
+                        'W' -> Ok White
+                        ' ' -> Ok None
+                        _ -> Err (InvalidChar char)
+    rowWidths = rows |> List.map List.len
+    width = rowWidths |> List.max |> Result.withDefault 0
+    if rowWidths |> List.any \w -> w != width then
+        Err BoardWasNotRectangular
+    else
+        height = List.len rows
+        Ok { rows, width, height }
+
+getStone : Board, Intersection -> Stone
+getStone = \board, { x, y } ->
+    board.rows |> List.get y |> Result.withDefault [] |> List.get x |> Result.withDefault None
+
+territory : Str, Intersection -> Result Territory [OutOfBounds, BoardWasEmpty, BoardWasNotRectangular, InvalidChar U8]
+territory = \boardStr, intersection ->
+    board = parse? boardStr
+    if intersection.x >= board.width || intersection.y >= board.height then
+        Err OutOfBounds
+        else
+
+    Ok (searchTerritory board intersection)
+
+searchTerritory : Board, Intersection -> Territory
+searchTerritory = \board, intersection ->
+    help = \toVisit, visited, surroundingStones ->
+        when toVisit is
+            [] -> { visited, surroundingStones }
+            [visiting, .. as restToVisit] ->
+                if visited |> Set.contains visiting then
+                    help restToVisit visited surroundingStones
+                    else
+
+                stone = board |> getStone visiting
+                when stone is
+                    Black | White ->
+                        newSurroundingStones = surroundingStones |> Set.insert stone
+                        help restToVisit visited newSurroundingStones
+
+                    None ->
+                        neighbors =
+                            [
+                                { x: visiting.x |> Num.subSaturated 1, y: visiting.y },
+                                { x: visiting.x + 1, y: visiting.y },
+                                { x: visiting.x, y: visiting.y |> Num.subSaturated 1 },
+                                { x: visiting.x, y: visiting.y + 1 },
+                            ]
+                            |> List.dropIf \neighbor ->
+                                neighbor.x >= board.width || neighbor.y >= board.height || neighbor == visiting
+                        newToVisit = restToVisit |> List.concat neighbors
+                        newVisited = visited |> Set.insert visiting
+                        help newToVisit newVisited surroundingStones
+    searchResult = help [intersection] (Set.empty {}) (Set.empty {})
+    if searchResult.visited |> Set.isEmpty then
+        { owner: None, territory: Set.empty {} }
+    else
+        owner =
+            if searchResult.surroundingStones == Set.single Black then
+                Black
+            else if searchResult.surroundingStones == Set.single White then
+                White
+            else
+                None
+        { owner, territory: searchResult.visited }
+
+territories : Str -> Result Territories [BoardWasEmpty, BoardWasNotRectangular, InvalidChar U8]
+territories = \boardStr ->
+    board = parse? boardStr
+    board.rows
+    |> List.mapWithIndex \row, y ->
+        row
+        |> List.mapWithIndex \stone, x ->
+            if stone == None then
+                [{ x, y }]
+            else
+                []
+        |> List.join
+    |> List.join
+    |> List.walk { black: Set.empty {}, white: Set.empty {}, none: Set.empty {} } \state, intersection ->
+        if state.black |> Set.contains intersection || state.white |> Set.contains intersection || state.none |> Set.contains intersection then
+            state
+        else
+            newTerritory = searchTerritory board intersection
+            when newTerritory.owner is
+                Black -> { black: state.black |> Set.union newTerritory.territory, white: state.white, none: state.none }
+                White -> { black: state.black, white: state.white |> Set.union newTerritory.territory, none: state.none }
+                None -> { black: state.black, white: state.white, none: state.none |> Set.union newTerritory.territory }
+    |> Ok
+

exercises/practice/go-counting/.meta/config.json

@@ -0,0 +1,17 @@
+{
+  "authors": [
+    "ageron"
+  ],
+  "files": {
+    "solution": [
+      "GoCounting.roc"
+    ],
+    "test": [
+      "go-counting-test.roc"
+    ],
+    "example": [
+      ".meta/Example.roc"
+    ]
+  },
+  "blurb": "Count the scored points on a Go board."
+}

exercises/practice/go-counting/.meta/template.j2

@@ -0,0 +1,57 @@
+{%- import "generator_macros.j2" as macros with context -%}
+{{ macros.canonical_ref() }}
+{{ macros.header() }}
+
+{% macro to_territory(territory) %}
+{%- if territory == [] %}
+Set.empty {}
+{%- else %}
+Set.fromList [
+{%- for intersection in territory %}
+    { x : {{ intersection[0] }}, y : {{ intersection[1] }} },
+{%- endfor %}
+]
+{%- endif %}
+{% endmacro %}
+
+import {{ exercise | to_pascal }} exposing [territory, territories]
+
+## The following two comparison functions are temporary workarounds for Roc issue #7144:
+## comparing tags or records containing sets sometimes returns the wrong result
+## depending on the internal order of the set data, so we have to unwrap the sets
+## in order to compare them properly.
+compareTerritory = \maybeResult, maybeExpected ->
+    when (maybeResult, maybeExpected) is
+      (Ok result, Ok expected) -> result.owner == expected.owner && result.territory == expected.territory
+      _ -> Bool.false
+
+compareTerritories = \maybeResult, maybeExpected ->
+    when (maybeResult, maybeExpected) is
+      (Ok result, Ok expected) -> result.black == expected.black && result.white == expected.white && result.none == expected.none
+      _ -> Bool.false
+
+{% for case in cases -%}
+# {{ case["description"] }}
+expect
+    board = {{ case["input"]["board"] | to_roc_multiline_string | replace(" ", "·") | indent(8) }} |> Str.replaceEach "·" " "
+    result = board |> {{ case["property"] | to_camel }}
+    {%- if case["property"] == "territory" %} { x : {{ case["input"]["x"] }}, y : {{ case["input"]["y"] }} }{% endif %}
+    {%- if case["expected"]["error"] %}
+    result |> Result.isErr
+    {%- elif case["expected"]["owner"] %}
+    expected = Ok {
+        owner: {{ case["expected"]["owner"] | to_pascal }},
+        territory: {{ to_territory(case["expected"]["territory"]) }},
+    }
+    result |> compareTerritory expected
+    {%- else %}
+    expected = Ok {
+        black: {{ to_territory(case["expected"]["territoryBlack"]) }},
+        white: {{ to_territory(case["expected"]["territoryWhite"]) }},
+        none: {{ to_territory(case["expected"]["territoryNone"]) }},
+    }
+    result |> compareTerritories expected
+    {%- endif %}
+
+
+{% endfor %}

exercises/practice/go-counting/.meta/tests.toml

@@ -0,0 +1,45 @@
+# 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.
+
+[94d0c01a-17d0-424c-aab5-2736d0da3939]
+description = "Black corner territory on 5x5 board"
+
+[b33bec54-356a-485c-9c71-1142a9403213]
+description = "White center territory on 5x5 board"
+
+[def7d124-422e-44ae-90e5-ceda09399bda]
+description = "Open corner territory on 5x5 board"
+
+[57d79036-2618-47f4-aa87-56c06d362e3d]
+description = "A stone and not a territory on 5x5 board"
+
+[0c84f852-e032-4762-9010-99f6a001da96]
+description = "Invalid because X is too low for 5x5 board"
+include = false
+
+[6f867945-9b2c-4bdd-b23e-b55fe2069a68]
+description = "Invalid because X is too high for 5x5 board"
+
+[d67aaffd-fdf1-4e7f-b9e9-79897402b64a]
+description = "Invalid because Y is too low for 5x5 board"
+include = false
+
+[14f23c25-799e-4371-b3e5-777a2c30357a]
+description = "Invalid because Y is too high for 5x5 board"
+
+[37fb04b5-98c1-4b96-8c16-af2d13624afd]
+description = "One territory is the whole board"
+
+[9a1c59b7-234b-495a-8d60-638489f0fc0a]
+description = "Two territory rectangular board"
+
+[d1645953-1cd5-4221-af6f-8164f96249e1]
+description = "Two region rectangular board"

exercises/practice/go-counting/GoCounting.roc

@@ -0,0 +1,24 @@
+module [territory, territories]
+
+Intersection : { x : U64, y : U64 }
+
+Stone : [White, Black, None]
+
+Territory : {
+    owner : Stone,
+    territory : Set Intersection,
+}
+
+Territories : {
+    black : Set Intersection,
+    white : Set Intersection,
+    none : Set Intersection,
+}
+
+territory : Str, Intersection -> Result Territory _
+territory = \boardStr, { x, y } ->
+    crash "Please implement the 'territory' function"
+
+territories : Str -> Result Territories _
+territories = \boardStr ->
+    crash "Please implement the 'territories' function"