Run-Length Encoding

Challenge Overview

Implement run-length encoding and decoding.

Visit the run-length-encoding exercise on Exercism to read the full instructions and download the exercise files.

Community Solutions

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The following are the top 3 community solutions by stars:

Solution 1 by @naartjie (⭐ 1) — View on Exercism
Solution 2 by @hongchangwu (⭐ 0) — View on Exercism
Solution 3 by @wvauclain (⭐ 0) — View on Exercism

Source: Exercism reasonml/run-length-encoding

💡 View Solution

let encode = s =>
  s
  |> Js.String.unsafeReplaceBy1([%re "/(.)\\1+/g"], (s, ch, _, _) =>
       Printf.sprintf("%d%s", String.length(s), ch)
     );

let decode = s =>
  s
  |> Js.String.unsafeReplaceBy2([%re "/(\\d+)(\\D)/g"], (_, len, ch, _, _) =>
       ch |> Js_string.repeat(len |> int_of_string)