Exercise: Run-length encoding (and decoding)

This is currently draft/unfinished/work-in-progress.

Author: kotp

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

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+# Instructions
+
+Write the function that uses the run-length encoding and decoding algorithms to encode and decode a string.
+
+Run-length encoding (RLE) is a simple form of data compression where runs of consecutive identical data elements are replaced with one data value and count.
+
+Example:
+
+"WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWB"  ->  "12WB12W3B24WB"
+
+RLE allows the original data to be perfectly reconstructed from the compressed data, which makes it a lossless data compression.
+
+Example:
+
+"AABCCCDEEEE"  ->  "2AB3CD4E"  ->  "AABCCCDEEEE"
+
+For simplicity, you can assume that the unencoded string will only contain the letters A through Z. (either upper or lower case) and whitespace.
+
+This means that the encoded data will not contain any numbers, so that any numbers contained within data to be decoded will always represent the count for the character that follows it.
+
+

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

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+{
+  "authors": [
+    "KOTP"
+  ],
+  "files": {
+    "solution": [
+      "run_length_encoding.vim"
+    ],
+    "test": [
+      "run_length_encoding.vader"
+    ],
+    "example": [
+      ".meta/example.vim"
+    ]
+  },
+  "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.vim

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+function decode:(string)
+  return substitute(a:string, '\d\+\(\D\)', '\=submatch(1) . repeat(submatch(1), str2nr(submatch(0)))', 'g')
+endfunction
+
+function encode:(string)
+  let size = 1
+  let result = ''
+  while size <= len(a:string)
+    let char = a:string[size-1]
+    let l:count = 1
+    while size+l:count <= len(a:string) && a:string[size+l:count-1] ==# char
+      let l:count += 1
+    endwhile
+    let result .= l:count . char
+    let size += l:count
+  endwhile
+  return result
+  endfunction

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

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+""
+"" Write a function that will perform the algorithm that is known as "run-length
+"" encoding".
+""
+"" Run-length encoding (RLE) is a simple form of data compression where runs of
+"" consecutive identical data elements are replaced with one data value and
+"" count.
+""
+"" Example:
+""
+"" "WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWB"  ->  "12WB12W3B24WB"
+""
+"" RLE allows the original data to be perfectly reconstructed from the
+"" compressed data, which makes it a lossless data compression.
+""
+"" Example:
+""
+"" "AABCCCDEEEE"  ->  "2AB3CD4E"  ->  "AABCCCDEEEE"
+""
+"" For simplicity, you can assume that the unencoded string will only contain
+"" the letters A through Z. (either upper or lower case) and whitespace.
+
+"" This means that the encoded data will not contain any numbers, so that any
+"" numbers contained within data to be decoded will always represent the count
+"" for the character that follows it.
+""
+function! RunLengthDecoding(name) abort
+  " your code goes here
+endfunction
+
+function! RunLengthEncoding(name) abort
+  " your code goes here
+endfunction

exercises/practice/run-length-encoding/run_length_encoding.vader

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+
+Execute (no name given):
+  let g:name = ''
+  let g:expected = "One for you, one for me."
+  AssertEqual g:expected, TwoFer(g:name)
+
+Execute (a name given):
+  let g:name = "Alice"
+  let g:expected = "One for Alice, one for me."
+  AssertEqual g:expected, TwoFer(g:name)
+
+Execute (another name given):
+  let g:name = "Bob"
+  let g:expected = "One for Bob, one for me."
+  AssertEqual g:expected, TwoFer(g:name)