Create a program that takes a single string as input, and returns the run length encoded value.
Run length encoding is a compression algorithm that takes runs of sequential items in a series of data points, replacing that run with a single instance of the data point and the number of elements in that run.
This compression algorithm can be fairly efficient for some types of data. For example bitmap images can be greatly reduced by using this method, however it would be a poor choice for English language text, since it’s uncommon for a charater to be repeated more than twice. This would be extremely inefficient as most words would double in length, such as horse, which becomes 1h1o1r1s1e.
Historically, RLE has been used to encode bitmap images in Windows 3.x. It was not a commonly used format, however it was used as the format of the startup screen. The algorithm is also used by fax machines, since the data they send is largely whitespace with small amounts of text on the page.
Given a string of uppercase characters in the range A-Z, replace runs of sequential characters with a single instance of that value preceded by the number of items in the run.
For example, if would take the sequence JJJTTWPPMMMMYYYYYYYYYVVVVVV the output would look like:
3J2T1W2P4M9Y6V
Write the encoder that turns string into their run length encoded versions.
Seems easy? How about doing the reverse, and decoding a run length string and expand it to its original format!
Load up the REPL with:
$ mix && iex -S mixThen you can test it with:
iex(1)> Runlength.encode "ASDF"
"1A1S1D1F"This repo has some tests, so you can easily run run them with
$ mix testIf you're only interested in the encoding tests, then do
$ mix test test/encode_test.exs