Add run-length-encoding exercise (#71)

config.json

@@ -306,6 +306,14 @@
         "prerequisites": [],
         "difficulty": 2
       },
+      {
+        "slug": "run-length-encoding",
+        "name": "Run-Length Encoding",
+        "uuid": "d83ea09c-39f9-4e00-9a74-3f1d3be262ac",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 7
+      },
       {
         "slug": "space-age",
         "name": "Space Age",

exercises/practice/run-length-encoding/.docs/instructions.md

@@ -0,0 +1,20 @@
+# Instructions
+
+Implement run-length encoding and decoding.
+
+Run-length encoding (RLE) is a simple form of data compression, where runs (consecutive data elements) are replaced by just one data value and count.
+
+For example we can represent the original 53 characters with only 13.
+
+```text
+"WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWB"  ->  "12WB12W3B24WB"
+```
+
+RLE allows the original data to be perfectly reconstructed from the compressed data, which makes it a lossless data compression.
+
+```text
+"AABCCCDEEEE"  ->  "2AB3CD4E"  ->  "AABCCCDEEEE"
+```
+
+For simplicity, you can assume that the unencoded string will only contain the letters A through Z (either lower or upper case) and whitespace.
+This way data to be encoded will never contain any numbers and numbers inside data to be decoded always represent the count for the following character.

exercises/practice/run-length-encoding/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "erikschierboom"
+  ],
+  "files": {
+    "solution": [
+      "run-length-encoding.ua"
+    ],
+    "test": [
+      "tests.ua"
+    ],
+    "example": [
+      ".meta/example.ua"
+    ]
+  },
+  "blurb": "Implement run-length encoding and decoding.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Run-length_encoding"
+}

exercises/practice/run-length-encoding/.meta/example.ua

@@ -0,0 +1,8 @@
+EncodeRun  ← |1 ⊂⊃(⨬(""|°⋕)>1.⧻|⊢)
+EncodeRuns ← |1 ⍜(-@\0|⊜□.)
+Encode     ← |1 /$"__" ⍚(EncodeRun) EncodeRuns
+
+IsDigit   ← |1 ×⊃(≥@0|≤@9)
+UpdateRun ← |2 + ⊙(×10) -@0
+DecodeRun ← 0 ⊂: ▽ ⨬(1|∘)±. :
+Decode    ← |1 ◌ ∧(⨬(DecodeRun|UpdateRun) IsDigit.) ⊙(0 "")

exercises/practice/run-length-encoding/.meta/tests.toml

@@ -0,0 +1,49 @@
+# 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.
+
+[ad53b61b-6ffc-422f-81a6-61f7df92a231]
+description = "run-length encode a string -> empty string"
+
+[52012823-b7e6-4277-893c-5b96d42f82de]
+description = "run-length encode a string -> single characters only are encoded without count"
+
+[b7868492-7e3a-415f-8da3-d88f51f80409]
+description = "run-length encode a string -> string with no single characters"
+
+[859b822b-6e9f-44d6-9c46-6091ee6ae358]
+description = "run-length encode a string -> single characters mixed with repeated characters"
+
+[1b34de62-e152-47be-bc88-469746df63b3]
+description = "run-length encode a string -> multiple whitespace mixed in string"
+
+[abf176e2-3fbd-40ad-bb2f-2dd6d4df721a]
+description = "run-length encode a string -> lowercase characters"
+
+[7ec5c390-f03c-4acf-ac29-5f65861cdeb5]
+description = "run-length decode a string -> empty string"
+
+[ad23f455-1ac2-4b0e-87d0-b85b10696098]
+description = "run-length decode a string -> single characters only"
+
+[21e37583-5a20-4a0e-826c-3dee2c375f54]
+description = "run-length decode a string -> string with no single characters"
+
+[1389ad09-c3a8-4813-9324-99363fba429c]
+description = "run-length decode a string -> single characters with repeated characters"
+
+[3f8e3c51-6aca-4670-b86c-a213bf4706b0]
+description = "run-length decode a string -> multiple whitespace mixed in string"
+
+[29f721de-9aad-435f-ba37-7662df4fb551]
+description = "run-length decode a string -> lowercase string"
+
+[2a762efd-8695-4e04-b0d6-9736899fbc16]
+description = "encode and then decode -> encode followed by decode gives original string"

exercises/practice/run-length-encoding/run-length-encoding.ua

@@ -0,0 +1,7 @@
+# Encode a string using run-length encoding
+# Ciphertext ? Plaintext
+Encode ← |1 ⊙(⍤ "Please implement Encode" 0)
+
+# Decode a string encoded with run-length encoding
+# Plaintext ? Ciphertext
+Decode ← |1 ⊙(⍤ "Please implement Decode" 0)

exercises/practice/run-length-encoding/tests.ua

@@ -0,0 +1,40 @@
+~ "run-length-encoding.ua" ~ Decode Encode
+
+# Encode empty string
+⍤⤙≍ "" Encode ""
+
+# Encode single characters only are encoded without count
+⍤⤙≍ "XYZ" Encode "XYZ"
+
+# Encode string with no single characters
+⍤⤙≍ "2A3B4C" Encode "AABBBCCCC"
+
+# Encode single characters mixed with repeated characters
+⍤⤙≍ "12WB12W3B24WB" Encode "WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWB"
+
+# Encode multiple whitespace mixed in string
+⍤⤙≍ "2 hs2q q2w2 " Encode "  hsqq qww  "
+
+# Encode lowercase characters
+⍤⤙≍ "2a3b4c" Encode "aabbbcccc"
+
+# Decode empty string
+⍤⤙≍ "" Decode ""
+
+# Decode single characters only
+⍤⤙≍ "XYZ" Decode "XYZ"
+
+# Decode string with no single characters
+⍤⤙≍ "AABBBCCCC" Decode "2A3B4C"
+
+# Decode single characters with repeated characters
+⍤⤙≍ "WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWB" Decode "12WB12W3B24WB"
+
+# Decode multiple whitespace mixed in string
+⍤⤙≍ "  hsqq qww  " Decode "2 hs2q q2w2 "
+
+# Decode lowercase string
+⍤⤙≍ "aabbbcccc" Decode "2a3b4c"
+
+# Encode followed by decode gives original string
+⍤⤙≍ "zzz ZZ  zZ" Decode Encode "zzz ZZ  zZ"