Add flatten-array exercise (#189)

Author: BNAndras

config.json

@@ -98,6 +98,14 @@
           "transforming"
         ]
       },
+      {
+        "slug": "flatten-array",
+        "name": "Flatten Array",
+        "uuid": "091cf652-212f-44a6-8187-1a3acdb922e3",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
+      },
       {
         "slug": "hello-world",
         "name": "Hello World",

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 write a function that accepts an arbitrarily-deep nested list-like structure and returns 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": [
+    "BNAndras"
+  ],
+  "files": {
+    "solution": [
+      "flatten_array.vim"
+    ],
+    "test": [
+      "flatten_array.vader"
+    ],
+    "example": [
+      ".meta/example.vim"
+    ]
+  },
+  "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/example.vim

@@ -0,0 +1,12 @@
+function! Flatten(array) abort
+    let l:results = []
+    for l:elem in a:array
+        if type(l:elem) == v:t_list
+            call extend(l:results, Flatten(l:elem))
+        elseif l:elem isnot v:null
+            call add(l:results, l:elem)
+        endif
+    endfor
+
+    return results
+endfunction

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/flatten_array.vader

@@ -0,0 +1,55 @@
+
+Execute (empty):
+  let g:array = []
+  let g:expected = []
+  AssertEqual g:expected, Flatten(g:array)
+
+Execute (no nesting):
+  let g:array = [0, 1, 2]
+  let g:expected = [0, 1, 2]
+  AssertEqual g:expected, Flatten(g:array)
+
+Execute (flattens a nested array):
+  let g:array = [[[]]]
+  let g:expected = []
+  AssertEqual g:expected, Flatten(g:array)
+
+Execute (flattens array with just integers present):
+  let g:array = [1, [2, 3, 4, 5, 6, 7], 8]
+  let g:expected = [1, 2, 3, 4, 5, 6, 7, 8]
+  AssertEqual g:expected, Flatten(g:array)
+
+Execute (5 level nesting):
+  let g:array = [0, 2, [[2, 3], 8, 100, 4, [[[50]]]], -2]
+  let g:expected = [0, 2, 2, 3, 8, 100, 4, 50, -2]
+  AssertEqual g:expected, Flatten(g:array)
+
+Execute (6 level nesting):
+  let g:array = [1, [2, [[3]], [4, [[5]]], 6, 7], 8]
+  let g:expected = [1, 2, 3, 4, 5, 6, 7, 8]
+  AssertEqual g:expected, Flatten(g:array)
+
+Execute (null values are omitted from the final result):
+  let g:array = [1, 2, v:null]
+  let g:expected = [1, 2]
+  AssertEqual g:expected, Flatten(g:array)
+
+Execute (consecutive null values at the front of the list are omitted from the final result):
+  let g:array = [v:null, v:null, 3]
+  let g:expected = [3]
+  AssertEqual g:expected, Flatten(g:array)
+
+Execute (consecutive null values in the middle of the list are omitted from the final result):
+  let g:array = [1, v:null, v:null, 4]
+  let g:expected = [1, 4]
+  AssertEqual g:expected, Flatten(g:array)
+
+Execute (6 level nest list with null values):
+  let g:array = [0, 2, [[2, 3], 8, [[100]], v:null, [[v:null]]], -2]
+  let g:expected = [0, 2, 2, 3, 8, 100, -2]
+  AssertEqual g:expected, Flatten(g:array)
+
+Execute (all values in nested list are null):
+  let g:array = [v:null, [[[v:null]]], v:null, v:null, [[v:null, v:null], v:null], v:null]
+  let g:expected = []
+  AssertEqual g:expected, Flatten(g:array)

exercises/practice/flatten-array/flatten_array.vim

@@ -0,0 +1,15 @@
+"
+" Flattens an arbitrarily-deep nested array, removing v:null values.
+"
+" Examples:
+"
+"   :echo Flatten([])
+"   []
+"   :echo Flatten([0, 1, 2])
+"   [0, 1, 2]
+"   :echo Flatten([0, 1, [2, 3, v:null]])
+"   [0, 1, 2, 3]
+"
+function! Flatten(array) abort
+  " your implemention goes here
+endfunction