Add flatten-array

config.json

@@ -224,6 +224,14 @@
         "prerequisites": [],
         "difficulty": 2
       },
+      {
+        "slug": "flatten-array",
+        "name": "Flatten Array",
+        "uuid": "963cd26f-59ef-4651-86a2-bb1018d32523",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 3
+      },
       {
         "slug": "prime-factors",
         "name": "Prime Factors",

exercises/practice/flatten-array/.docs/instructions.md

@@ -0,0 +1,11 @@
+# Instructions
+
+Take a nested list and return a single flattened list with all values except nil/null.
+
+The challenge is to take an arbitrarily-deep nested list-like structure and produce a flattened structure without any nil/null values.
+
+For example:
+
+input: [1,[2,3,null,4],[null],5]
+
+output: [1,2,3,4,5]

exercises/practice/flatten-array/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "src/FlattenArray.idr"
+    ],
+    "test": [
+      "test/src/Main.idr"
+    ],
+    "example": [
+      "example/FlattenArray.idr"
+    ]
+  },
+  "blurb": "Take a nested list and return a single list with all values except nil/null.",
+  "source": "Interview Question",
+  "source_url": "https://reference.wolfram.com/language/ref/Flatten.html"
+}

exercises/practice/flatten-array/.meta/tests.toml

@@ -0,0 +1,43 @@
+# 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.
+
+[8c71dabd-da60-422d-a290-4a571471fb14]
+description = "empty"
+
+[d268b919-963c-442d-9f07-82b93f1b518c]
+description = "no nesting"
+
+[3f15bede-c856-479e-bb71-1684b20c6a30]
+description = "flattens a nested array"
+
+[c84440cc-bb3a-48a6-862c-94cf23f2815d]
+description = "flattens array with just integers present"
+
+[d3d99d39-6be5-44f5-a31d-6037d92ba34f]
+description = "5 level nesting"
+
+[d572bdba-c127-43ed-bdcd-6222ac83d9f7]
+description = "6 level nesting"
+
+[0705a8e5-dc86-4cec-8909-150c5e54fa9c]
+description = "null values are omitted from the final result"
+
+[c6cf26de-8ccd-4410-84bd-b9efd88fd2bc]
+description = "consecutive null values at the front of the list are omitted from the final result"
+
+[382c5242-587e-4577-b8ce-a5fb51e385a1]
+description = "consecutive null values in the middle of the list are omitted from the final result"
+
+[ef1d4790-1b1e-4939-a179-51ace0829dbd]
+description = "6 level nest list with null values"
+
+[85721643-705a-4150-93ab-7ae398e2942d]
+description = "all values in nested list are null"

exercises/practice/flatten-array/example/FlattenArray.idr

@@ -0,0 +1,11 @@
+module FlattenArray
+
+public export
+data Tree a = Hollow | Leaf a | Branch (List (Tree a))
+
+export
+flatten : Tree a -> List a
+flatten Hollow = []
+flatten (Leaf n) = [n]
+flatten (Branch []) = []
+flatten (Branch (x::xs)) = (flatten x) ++ (flatten (Branch xs))

exercises/practice/flatten-array/flatten-array.ipkg

@@ -0,0 +1,3 @@
+package flatten-array
+modules = FlattenArray
+sourcedir = "src"

exercises/practice/flatten-array/pack.toml

@@ -0,0 +1,10 @@
+[custom.all.flatten-array]
+type = "local"
+path = "."
+ipkg = "flatten-array.ipkg"
+test = "test/test.ipkg"
+
+[custom.all.flatten-array-test]
+type = "local"
+path = "test"
+ipkg = "test.ipkg"

exercises/practice/flatten-array/src/FlattenArray.idr

@@ -0,0 +1,8 @@
+module FlattenArray
+
+public export
+data Tree a = Hollow | Leaf a | Branch (List (Tree a))
+
+export
+flatten : Tree a -> List a
+flatten tree = ?flatten_rhs

exercises/practice/flatten-array/test/src/Main.idr

@@ -0,0 +1,30 @@
+module Main
+
+import System
+import Tester
+import Tester.Runner
+
+import FlattenArray
+
+tests : List Test
+tests =
+  [ test "empty"                                                                               (assertEq (flatten $ Branch []) [])
+  , test "no nesting"                                                                          (assertEq (flatten $ Branch [Leaf 0, Leaf 1, Leaf 2]) [0, 1, 2])
+  , test "flattens a nested array"                                                             (assertEq (flatten $ Branch [Branch [Branch []]]) [])
+  , test "flattens array with just integers present"                                           (assertEq (flatten $ Branch [Leaf 1, Branch [Leaf 2, Leaf 3, Leaf 4, Leaf 5, Leaf 6, Leaf 7], Leaf 8]) [1, 2, 3, 4, 5, 6, 7, 8])
+  , test "5 level nesting"                                                                     (assertEq (flatten $ Branch [Leaf 0, Leaf 2, Branch [Branch [Leaf 2, Leaf 3], Leaf 8, Leaf 100, Leaf 4, Branch [Branch [Branch [Leaf 50]]]], Leaf (-2)]) [0, 2, 2, 3, 8, 100, 4, 50, -2])
+  , test "6 level nesting"                                                                     (assertEq (flatten $ Branch [Leaf 1, Branch [Leaf 2, Branch [Branch [Leaf 3]], Branch [Leaf 4, Branch [Branch [Leaf 5]]], Leaf 6, Leaf 7], Leaf 8]) [1, 2, 3, 4, 5, 6, 7, 8])
+  , test "null values are omitted from the final result"                                       (assertEq (flatten $ Branch [Leaf 1, Leaf 2, Hollow]) [1, 2])
+  , test "consecutive null values at the front of the list are omitted from the final result"  (assertEq (flatten $ Branch [Hollow, Hollow, Leaf 3]) [3])
+  , test "consecutive null values in the middle of the list are omitted from the final result" (assertEq (flatten $ Branch [Leaf 1, Hollow, Hollow, Leaf 4]) [1, 4])
+  , test "6 level nest list with null values"                                                  (assertEq (flatten $ Branch [Leaf 0, Leaf 2, Branch [Branch [Leaf 2, Leaf 3], Leaf 8, Branch [Branch [Leaf 100]], Hollow, Branch [Branch [Hollow]]], Leaf (-2)]) [0, 2, 2, 3, 8, 100, -2])
+  , test "all values in nested list are null"                                                  (assertEq (flatten $ Branch [Hollow, Branch [Branch [Branch [Hollow]]], Hollow, Hollow, Branch [Branch [Hollow, Hollow], Hollow], Hollow]) [])
+  ]
+
+export
+main : IO ()
+main = do
+  success <- runTests tests
+  if success
+     then putStrLn "All tests passed"
+     else exitFailure

exercises/practice/flatten-array/test/test.ipkg

@@ -0,0 +1,6 @@
+package flatten-array-test
+depends = flatten-array
+  , tester
+main = Main
+executable = "flatten-array-test"
+sourcedir = "src"

generators/exercises/flatten_array.py

@@ -0,0 +1,14 @@
+
+def generate_test(case):
+    def to_tree(data):
+        if data is None:
+            return "Hollow"
+        if isinstance(data, list):
+            return "Branch " + str(list(map(to_tree, data))).replace("'", "")
+        if data < 0:
+            data = f"({data})"
+        return f"Leaf {data}"
+    property = case["property"]
+    expected = case["expected"]
+    tree = to_tree(case["input"]["array"])
+    return f'assertEq ({property} $ {tree}) {expected}'