Rosetta Code

Run-length encoding

Encode and decode a short sample string with classic run-length encoding.

Edit the source, then Run. Checks start after your first Run. Ctrl/⌘ + Enter runs; Tab indents. Preview services use sample data and never contact a real service.

Sourcerosettacode/popular/run_length_encoding.vibe
type RunResult = { decoded: string, encoded: array<{ char: string, count: int }>, sample: string }

def encode(text: string) -> array<{ char: string, count: int }>
  if text == ""
    return []
  end

  output: array<{ char: string, count: int }> = []
  current = text.chars.fetch(0)
  count = 1
  index = 1

  while index < text.length
    char = text.chars.fetch(index)

    if char == current
      count = count + 1
    else
      output.push({
        char: current,
        count: count
      })
      current = char
      count = 1
    end

    index = index + 1
  end

  output.push({
    char: current,
    count: count
  })
end

def decode(runs: array<{ char: string, count: int }>) -> string
  output = ""
  index = 0

  while index < runs.length
    entry = runs.fetch(index)
    entry["count"].times {
      output = output + entry["char"]
    }

    index = index + 1
  end

  output
end

def run -> RunResult
  sample = "AAABBCCCC"
  encoded = encode(sample)
  {
    sample: sample,
    encoded: encoded,
    decoded: decode(encoded)
  }
end

Output

Click Run example to see the result.

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