Add run-length-encoding exercise

config.json

@@ -572,6 +572,14 @@
         "prerequisites": [],
         "difficulty": 1
       },
+      {
+        "slug": "run-length-encoding",
+        "name": "Run-Length Encoding",
+        "uuid": "a1b3d36c-5745-49f6-84d8-4025b3826344",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 3
+      },
       {
         "slug": "saddle-points",
         "name": "Saddle Points",

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": [
+    "glennj"
+  ],
+  "files": {
+    "solution": [
+      "lib/RunLengthEncoding.pm"
+    ],
+    "test": [
+      "t/run-length-encoding.t"
+    ],
+    "example": [
+      ".meta/solutions/lib/RunLengthEncoding.pm"
+    ]
+  },
+  "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/solutions/lib/RunLengthEncoding.pm

@@ -0,0 +1,20 @@
+package RunLengthEncoding;
+
+use strict;
+use warnings;
+use experimental qw<signatures postderef postderef_qq>;
+
+use Exporter qw<import>;
+our @EXPORT_OK = qw<encode decode>;
+
+sub encode ($string) {
+    ( my $encoded = $string ) =~ s{(.)(\1+)}{(1 + length $2) . $1}ge;
+    return $encoded;
+}
+
+sub decode ($string) {
+    ( my $decoded = $string ) =~ s{(\d+)(.)}{$2 x $1}ge;
+    return $decoded;
+}
+
+1;

exercises/practice/run-length-encoding/.meta/solutions/t/run-length-encoding.t

@@ -0,0 +1 @@
+../../../t/run-length-encoding.t

exercises/practice/run-length-encoding/.meta/template-data.yaml

@@ -0,0 +1,55 @@
+subs: encode decode
+
+properties:
+  encode:
+    test: |-
+      use Data::Dmp;
+      sprintf(<<'END', map {dmp $_} ($case->{input}{string}, $case->@{qw<expected description>}));
+      is(
+          encode(%s),
+          %s,
+          %s,
+      );
+      END
+
+  decode:
+    test: |-
+      use Data::Dmp;
+      sprintf(<<'END', map {dmp $_} ($case->{input}{string}, $case->@{qw<expected description>}));
+      is(
+          decode(%s),
+          %s,
+          %s,
+      );
+      END
+
+  consistency:
+    test: |-
+      use Data::Dmp;
+      sprintf(<<'END', map {dmp $_} ($case->{input}{string}, $case->@{qw<expected description>}));
+      is(
+          decode(encode(%s)),
+          %s,
+          %s,
+      );
+      END
+
+example: |-
+  sub encode ($string) {
+    (my $encoded = $string) =~ s{(.)(\1+)}{(1 + length $2) . $1}ge;
+    return $encoded;
+  }
+
+  sub decode ($string) {
+    (my $decoded = $string) =~ s{(\d+)(.)}{$2 x $1}ge;
+    return $decoded;
+  }
+
+stub: |-
+  sub encode ($string) {
+    return undef;
+  }
+
+  sub decode ($string) {
+    return undef;
+  }

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/lib/RunLengthEncoding.pm

@@ -0,0 +1,16 @@
+package RunLengthEncoding;
+
+use v5.40;
+
+use Exporter qw<import>;
+our @EXPORT_OK = qw<encode decode>;
+
+sub encode ($string) {
+    return undef;
+}
+
+sub decode ($string) {
+    return undef;
+}
+
+1;

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

@@ -0,0 +1,87 @@
+#!/usr/bin/env perl
+use Test2::V0;
+
+use FindBin qw<$Bin>;
+use lib "$Bin/../lib", "$Bin/../local/lib/perl5";
+
+use RunLengthEncoding qw<encode decode>;
+
+is( # begin: ad53b61b-6ffc-422f-81a6-61f7df92a231
+    encode(""),
+    "",
+    "run-length encode a string: empty string",
+); # end: ad53b61b-6ffc-422f-81a6-61f7df92a231
+
+is( # begin: 52012823-b7e6-4277-893c-5b96d42f82de
+    encode("XYZ"),
+    "XYZ",
+    "run-length encode a string: single characters only are encoded without count",
+); # end: 52012823-b7e6-4277-893c-5b96d42f82de
+
+is( # begin: b7868492-7e3a-415f-8da3-d88f51f80409
+    encode("AABBBCCCC"),
+    "2A3B4C",
+    "run-length encode a string: string with no single characters",
+); # end: b7868492-7e3a-415f-8da3-d88f51f80409
+
+is( # begin: 859b822b-6e9f-44d6-9c46-6091ee6ae358
+    encode("WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWB"),
+    "12WB12W3B24WB",
+    "run-length encode a string: single characters mixed with repeated characters",
+); # end: 859b822b-6e9f-44d6-9c46-6091ee6ae358
+
+is( # begin: 1b34de62-e152-47be-bc88-469746df63b3
+    encode("  hsqq qww  "),
+    "2 hs2q q2w2 ",
+    "run-length encode a string: multiple whitespace mixed in string",
+); # end: 1b34de62-e152-47be-bc88-469746df63b3
+
+is( # begin: abf176e2-3fbd-40ad-bb2f-2dd6d4df721a
+    encode("aabbbcccc"),
+    "2a3b4c",
+    "run-length encode a string: lowercase characters",
+); # end: abf176e2-3fbd-40ad-bb2f-2dd6d4df721a
+
+is( # begin: 7ec5c390-f03c-4acf-ac29-5f65861cdeb5
+    decode(""),
+    "",
+    "run-length decode a string: empty string",
+); # end: 7ec5c390-f03c-4acf-ac29-5f65861cdeb5
+
+is( # begin: ad23f455-1ac2-4b0e-87d0-b85b10696098
+    decode("XYZ"),
+    "XYZ",
+    "run-length decode a string: single characters only",
+); # end: ad23f455-1ac2-4b0e-87d0-b85b10696098
+
+is( # begin: 21e37583-5a20-4a0e-826c-3dee2c375f54
+    decode("2A3B4C"),
+    "AABBBCCCC",
+    "run-length decode a string: string with no single characters",
+); # end: 21e37583-5a20-4a0e-826c-3dee2c375f54
+
+is( # begin: 1389ad09-c3a8-4813-9324-99363fba429c
+    decode("12WB12W3B24WB"),
+    "WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWB",
+    "run-length decode a string: single characters with repeated characters",
+); # end: 1389ad09-c3a8-4813-9324-99363fba429c
+
+is( # begin: 3f8e3c51-6aca-4670-b86c-a213bf4706b0
+    decode("2 hs2q q2w2 "),
+    "  hsqq qww  ",
+    "run-length decode a string: multiple whitespace mixed in string",
+); # end: 3f8e3c51-6aca-4670-b86c-a213bf4706b0
+
+is( # begin: 29f721de-9aad-435f-ba37-7662df4fb551
+    decode("2a3b4c"),
+    "aabbbcccc",
+    "run-length decode a string: lowercase string",
+); # end: 29f721de-9aad-435f-ba37-7662df4fb551
+
+is( # begin: 2a762efd-8695-4e04-b0d6-9736899fbc16
+    decode( encode("zzz ZZ  zZ") ),
+    "zzz ZZ  zZ",
+    "encode and then decode: encode followed by decode gives original string",
+); # end: 2a762efd-8695-4e04-b0d6-9736899fbc16
+
+done_testing;