Add killer-sudoku-helper tests

config.json

@@ -2662,6 +2662,19 @@
           "while-loops"
         ],
         "difficulty": 2
+      },
+      {
+        "slug": "killer-sudoku-helper",
+        "name": "Killer Sudoku Helper",
+        "uuid": "ef287b7e-50ca-4072-93e8-84efbbe77079",
+        "practices": [
+          "arrays"
+        ],
+        "prerequisites": [
+          "arrays",
+          "numbers"
+        ],
+        "difficulty": 7
       }
     ],
     "foregone": [

exercises/Exercises.sln

@@ -347,6 +347,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "EliudsEggs", "practice\eliu
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Knapsack", "practice\knapsack\Knapsack.csproj", "{90C70CAA-A225-4D66-8B42-6AC82AD1D5DC}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "KillerSudokuHelper", "practice\killer-sudoku-helper\KillerSudokuHelper.csproj", "{BEBBD420-075D-46F1-AE51-CC9A05FECE4A}"
+EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "SquareRoot", "practice\square-root\SquareRoot.csproj", "{5C05051E-D46C-4544-9CF8-F2A748F63172}"
 EndProject
 Global
@@ -1039,6 +1041,10 @@ Global
 		{5C05051E-D46C-4544-9CF8-F2A748F63172}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{5C05051E-D46C-4544-9CF8-F2A748F63172}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{5C05051E-D46C-4544-9CF8-F2A748F63172}.Release|Any CPU.Build.0 = Release|Any CPU
+		{BEBBD420-075D-46F1-AE51-CC9A05FECE4A}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{BEBBD420-075D-46F1-AE51-CC9A05FECE4A}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{BEBBD420-075D-46F1-AE51-CC9A05FECE4A}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{BEBBD420-075D-46F1-AE51-CC9A05FECE4A}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -1215,6 +1221,7 @@ Global
 		{2F3B7384-F4CA-4925-B07C-E05DB3FAC01B} = {E276EF69-669A-43E0-88AC-8ABB17A9C026}
 		{90C70CAA-A225-4D66-8B42-6AC82AD1D5DC} = {E276EF69-669A-43E0-88AC-8ABB17A9C026}
 		{5C05051E-D46C-4544-9CF8-F2A748F63172} = {E276EF69-669A-43E0-88AC-8ABB17A9C026}
+		{BEBBD420-075D-46F1-AE51-CC9A05FECE4A} = {E276EF69-669A-43E0-88AC-8ABB17A9C026}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {AB4EA6C9-5461-4024-BDC7-2AE0C3A85CD1}

exercises/practice/killer-sudoku-helper/.docs/instructions.md

@@ -0,0 +1,85 @@
+# Instructions
+
+A friend of yours is learning how to solve Killer Sudokus (rules below) but struggling to figure out which digits can go in a cage.
+They ask you to help them out by writing a small program that lists all valid combinations for a given cage, and any constraints that affect the cage.
+
+To make the output of your program easy to read, the combinations it returns must be sorted.
+
+## Killer Sudoku Rules
+
+- [Standard Sudoku rules][sudoku-rules] apply.
+- The digits in a cage, usually marked by a dotted line, add up to the small number given in the corner of the cage.
+- A digit may only occur once in a cage.
+
+For a more detailed explanation, check out [this guide][killer-guide].
+
+## Example 1: Cage with only 1 possible combination
+
+In a 3-digit cage with a sum of 7, there is only one valid combination: 124.
+
+- 1 + 2 + 4 = 7
+- Any other combination that adds up to 7, e.g. 232, would violate the rule of not repeating digits within a cage.
+
+![Sudoku grid, with three killer cages that are marked as grouped together.
+The first killer cage is in the 3×3 box in the top left corner of the grid.
+The middle column of that box forms the cage, with the followings cells from top to bottom: first cell contains a 1 and a pencil mark of 7, indicating a cage sum of 7, second cell contains a 2, third cell contains a 5.
+The numbers are highlighted in red to indicate a mistake.
+The second killer cage is in the central 3×3 box of the grid.
+The middle column of that box forms the cage, with the followings cells from top to bottom: first cell contains a 1 and a pencil mark of 7, indicating a cage sum of 7, second cell contains a 2, third cell contains a 4.
+None of the numbers in this cage are highlighted and therefore don't contain any mistakes.
+The third killer cage follows the outside corner of the central 3×3 box of the grid.
+It is made up of the following three cells: the top left cell of the cage contains a 2, highlighted in red, and a cage sum of 7.
+The top right cell of the cage contains a 3.
+The bottom right cell of the cage contains a 2, highlighted in red. All other cells are empty.][one-solution-img]
+
+## Example 2: Cage with several combinations
+
+In a 2-digit cage with a sum 10, there are 4 possible combinations:
+
+- 19
+- 28
+- 37
+- 46
+
+![Sudoku grid, all squares empty except for the middle column, column 5, which has 8 rows filled.
+Each continguous two rows form a killer cage and are marked as grouped together.
+From top to bottom: first group is a cell with value 1 and a pencil mark indicating a cage sum of 10, cell with value 9.
+Second group is a cell with value 2 and a pencil mark of 10, cell with value 8.
+Third group is a cell with value 3 and a pencil mark of 10, cell with value 7.
+Fourth group is a cell with value 4 and a pencil mark of 10, cell with value 6.
+The last cell in the column is empty.][four-solutions-img]
+
+## Example 3: Cage with several combinations that is restricted
+
+In a 2-digit cage with a sum 10, where the column already contains a 1 and a 4, there are 2 possible combinations:
+
+- 28
+- 37
+
+19 and 46 are not possible due to the 1 and 4 in the column according to standard Sudoku rules.
+
+![Sudoku grid, all squares empty except for the middle column, column 5, which has 8 rows filled.
+The first row contains a 4, the second is empty, and the third contains a 1.
+The 1 is highlighted in red to indicate a mistake.
+The last 6 rows in the column form killer cages of two cells each.
+From top to bottom: first group is a cell with value 2 and a pencil mark indicating a cage sum of 10, cell with value 8.
+Second group is a cell with value 3 and a pencil mark of 10, cell with value 7.
+Third group is a cell with value 1, highlighted in red, and a pencil mark of 10, cell with value 9.][not-possible-img]
+
+## Trying it yourself
+
+If you want to give an approachable Killer Sudoku a go, you can try out [this puzzle][clover-puzzle] by Clover, featured by [Mark Goodliffe on Cracking The Cryptic on the 21st of June 2021][goodliffe-video].
+
+You can also find Killer Sudokus in varying difficulty in numerous newspapers, as well as Sudoku apps, books and websites.
+
+## Credit
+
+The screenshots above have been generated using [F-Puzzles.com](https://www.f-puzzles.com/), a Puzzle Setting Tool by Eric Fox.
+
+[sudoku-rules]: https://masteringsudoku.com/sudoku-rules-beginners/
+[killer-guide]: https://masteringsudoku.com/killer-sudoku/
+[one-solution-img]: https://assets.exercism.org/images/exercises/killer-sudoku-helper/example1.png
+[four-solutions-img]: https://assets.exercism.org/images/exercises/killer-sudoku-helper/example2.png
+[not-possible-img]: https://assets.exercism.org/images/exercises/killer-sudoku-helper/example3.png
+[clover-puzzle]: https://app.crackingthecryptic.com/sudoku/HqTBn3Pr6R
+[goodliffe-video]: https://youtu.be/c_NjEbFEeW0?t=1180

exercises/practice/killer-sudoku-helper/.editorconfig

@@ -0,0 +1,141 @@
+###############################
+# Core EditorConfig Options   #
+###############################
+
+; This file is for unifying the coding style for different editors and IDEs.
+; More information at:
+; https://docs.microsoft.com/en-us/visualstudio/ide/editorconfig-code-style-settings-reference?view=vs-2017
+; https://docs.microsoft.com/en-us/visualstudio/ide/create-portable-custom-editor-options?view=vs-2017
+
+root = true
+
+[*]
+indent_style = space
+
+[KillerSudokuHelper.cs]
+indent_size = 4
+
+###############################
+# .NET Coding Conventions     #
+###############################
+
+# Organize usings
+dotnet_sort_system_directives_first = true
+dotnet_separate_import_directive_groups = true
+
+# this. preferences
+dotnet_style_qualification_for_field = false:suggestion
+dotnet_style_qualification_for_property = false:suggestion
+dotnet_style_qualification_for_method = false:suggestion
+dotnet_style_qualification_for_event = false:suggestion
+
+# Language keywords vs BCL types preferences
+dotnet_style_predefined_type_for_locals_parameters_members = true:suggestion
+dotnet_style_predefined_type_for_member_access = true:suggestion
+
+# Parentheses preferences
+dotnet_style_parentheses_in_arithmetic_binary_operators = never_if_unnecessary:none
+dotnet_style_parentheses_in_relational_binary_operators = never_if_unnecessary:none
+dotnet_style_parentheses_in_other_binary_operators = never_if_unnecessary:none
+dotnet_style_parentheses_in_other_operators = never_if_unnecessary:suggestion
+
+# Modifier preferences
+dotnet_style_require_accessibility_modifiers = always:suggestion
+dotnet_style_readonly_field = true:suggestion
+
+# Expression-level preferences
+dotnet_style_object_initializer = true:suggestion
+dotnet_style_collection_initializer = true:suggestion
+dotnet_style_explicit_tuple_names = true:suggestion
+dotnet_style_prefer_inferred_tuple_names = true:suggestion
+dotnet_style_prefer_inferred_anonymous_type_member_names = true:suggestion
+dotnet_style_prefer_auto_properties = true:suggestion
+dotnet_style_prefer_is_null_check_over_reference_equality_method = true:suggestion
+dotnet_style_prefer_conditional_expression_over_assignment = true:suggestion
+dotnet_style_prefer_conditional_expression_over_return = true:suggestion
+dotnet_style_coalesce_expression = true:suggestion
+dotnet_style_null_propagation = true:suggestion
+
+###############################
+# Naming Conventions          #
+###############################
+
+# Style Definitions
+dotnet_naming_style.pascal_case_style.capitalization = pascal_case
+
+# Use PascalCase for constant fields
+dotnet_naming_rule.constant_fields_should_be_pascal_case.severity = suggestion
+dotnet_naming_rule.constant_fields_should_be_pascal_case.symbols = constant_fields
+dotnet_naming_rule.constant_fields_should_be_pascal_case.style = pascal_case_style
+dotnet_naming_symbols.constant_fields.applicable_kinds = field
+dotnet_naming_symbols.constant_fields.applicable_accessibilities = *
+dotnet_naming_symbols.constant_fields.required_modifiers = const
+
+###############################
+# C# Code Style Rules         #
+###############################
+
+# var preferences
+csharp_style_var_for_built_in_types = true:none
+csharp_style_var_when_type_is_apparent = true:none
+csharp_style_var_elsewhere = true:none
+
+# Expression-bodied members
+csharp_style_expression_bodied_methods = true:suggestion
+csharp_style_expression_bodied_constructors = true:suggestion
+csharp_style_expression_bodied_operators = true:suggestion
+csharp_style_expression_bodied_properties = true:suggestion
+csharp_style_expression_bodied_indexers = true:suggestion
+csharp_style_expression_bodied_accessors = true:suggestion
+
+# Pattern-matching preferences
+csharp_style_pattern_matching_over_is_with_cast_check = true:suggestion
+csharp_style_pattern_matching_over_as_with_null_check = true:suggestion
+
+# Null-checking preferences
+csharp_style_throw_expression = true:suggestion
+csharp_style_conditional_delegate_call = true:suggestion
+
+# Modifier preferences
+csharp_preferred_modifier_order = public,private,protected,internal,static,extern,new,virtual,abstract,sealed,override,readonly,unsafe,volatile,async:suggestion
+
+# Expression-level preferences
+csharp_prefer_braces = true:none
+csharp_prefer_simple_default_expression = true:suggestion
+csharp_style_deconstructed_variable_declaration = true:suggestion
+csharp_style_pattern_local_over_anonymous_function = true:suggestion
+csharp_style_inlined_variable_declaration = true:suggestion
+
+###############################
+# C# Formatting Rules         #
+###############################
+
+# New line preferences
+csharp_new_line_before_open_brace = all
+csharp_new_line_before_else = true
+csharp_new_line_before_catch = true
+csharp_new_line_before_finally = true
+csharp_new_line_before_members_in_object_initializers = false
+csharp_new_line_before_members_in_anonymous_types = false
+csharp_new_line_between_query_expression_clauses = true
+
+# Indentation preferences
+csharp_indent_case_contents = true
+csharp_indent_switch_labels = true
+csharp_indent_labels = flush_left
+
+# Space preferences
+csharp_space_after_cast = false
+csharp_space_after_keywords_in_control_flow_statements = true
+csharp_space_between_method_declaration_parameter_list_parentheses = false
+csharp_space_between_method_call_parameter_list_parentheses = false
+csharp_space_before_colon_in_inheritance_clause = true
+csharp_space_after_colon_in_inheritance_clause = true
+csharp_space_around_binary_operators = before_and_after
+csharp_space_between_method_declaration_empty_parameter_list_parentheses = false
+csharp_space_between_method_call_name_and_opening_parenthesis = false
+csharp_space_between_method_call_empty_parameter_list_parentheses = false
+
+# Wrapping preferences
+csharp_preserve_single_line_blocks = true
+csharp_preserve_single_line_statements = true

exercises/practice/killer-sudoku-helper/.meta/Example.cs

@@ -0,0 +1,38 @@
+using System.Collections.Generic;
+using System.Linq;
+
+public static class KillerSudokuHelper
+{
+    private static readonly int[] Digits = [1, 2, 3, 4, 5, 6, 7, 8, 9];
+
+    public static IEnumerable<int[]> Combinations(int sum, int size, int[] exclude) =>
+        Digits.Except(exclude).ToArray()
+            .Combinations(size)
+            .Where(comb => comb.Sum() == sum);
+
+    private static IEnumerable<T[]> Combinations<T>(this T[] items, int size)
+    {
+        if (size > items.Length) yield break;
+
+        var pool = items.ToArray();
+        var indices = Enumerable.Range(0, size).ToArray();
+
+        yield return indices.Select(x => pool[x]).ToArray();
+
+        while (true)
+        {
+            var i = indices.Length - 1;
+            while (i >= 0 && indices[i] == i + items.Length - size)
+                i -= 1;
+
+            if (i < 0) yield break;
+
+            indices[i] += 1;
+
+            for (var j = i + 1; j < size; j += 1)
+                indices[j] = indices[j - 1] + 1;
+
+            yield return indices.Select(x => pool[x]).ToArray();
+        }
+    }
+}

exercises/practice/killer-sudoku-helper/.meta/Generator.tpl

@@ -0,0 +1,21 @@
+using Xunit;
+
+public class {{ testClass }}
+{
+    {{- for test in tests }}
+    [Fact{{ if !for.first }}(Skip = "Remove this Skip property to run this test"){{ end }}]
+    public void {{ test.testMethod }}()
+    {
+        {{- if test.expected | array.size > 1 }}
+        int[][] expected = [
+        {{- for row in test.expected }}
+            {{ row }}{{- if !for.last }},{{ end -}}
+        {{ end }}
+        ];
+        {{- else }}
+        int[][] expected = {{ test.expected }};
+        {{ end -}}
+        Assert.Equal(expected, {{ testedClass }}.{{ test.testedMethod }}({{ test.input.cage.sum }}, {{ test.input.cage.size }}, {{ test.input.cage.exclude }}));
+    }
+    {{ end -}}
+}

exercises/practice/killer-sudoku-helper/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "erikschierboom"
+  ],
+  "files": {
+    "solution": [
+      "KillerSudokuHelper.cs"
+    ],
+    "test": [
+      "KillerSudokuHelperTests.cs"
+    ],
+    "example": [
+      ".meta/Example.cs"
+    ]
+  },
+  "blurb": "Write a tool that makes it easier to solve Killer Sudokus",
+  "source": "Created by Sascha Mann, Jeremy Walker, and BethanyG for the Julia track on Exercism.",
+  "source_url": "https://github.com/exercism/julia/pull/413"
+}