Created
June 9, 2017 07:56
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Elixir - Run-length (Encode/Decode)
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| defmodule Runlength do | |
| def encode(""), do: "" | |
| def encode(<<head :: binary-size(1), tail :: binary>>) do | |
| do_encode("", head, tail) | |
| end | |
| defp do_encode(result, acc = <<head :: binary-size(1), _ :: binary>>, "") do | |
| result <> Integer.to_string(String.length(acc)) <> head | |
| end | |
| defp do_encode(result, | |
| acc = <<head_1 :: binary-size(1), rest_1 :: binary>>, | |
| <<head_2 :: binary-size(1), rest_2 :: binary >>) do | |
| if head_1 == head_2 do | |
| do_encode(result, head_1 <> rest_1 <> head_2, rest_2) | |
| else | |
| do_encode( | |
| result <> Integer.to_string(String.length(acc)) <> head_1, | |
| head_2, | |
| rest_2 | |
| ) | |
| end | |
| end | |
| def decode(<<length :: binary-size(1), character :: binary-size(1), rest :: binary>>) do | |
| do_decode("", {length, character}, rest) | |
| end | |
| defp do_decode(acc, {length, character}, "") do | |
| acc <> String.duplicate(character, String.to_integer(length)) | |
| end | |
| defp do_decode(acc, | |
| {length, character}, | |
| <<length2 :: binary-size(1), | |
| character2 :: binary-size(1), | |
| rest :: binary>>) do | |
| do_decode(acc <> String.duplicate(character, String.to_integer(length)), {length2, character2}, rest) | |
| end | |
| end |
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