40 lines
1.1 KiB
Elixir
40 lines
1.1 KiB
Elixir
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defmodule Day18Part1 do
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def run do
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File.stream!("input")
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|> Stream.map(&parse_line/1)
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|> Stream.map(&evaluate/1)
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|> Enum.sum()
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|> IO.puts()
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end
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def parse_line(line) do
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line
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|> String.graphemes()
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|> Stream.reject(fn char -> char in [" ", "\n"] end)
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|> Enum.map(fn
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"*" -> :multiply
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"+" -> :add
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"(" -> :start_group
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")" -> :end_group
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num -> String.to_integer(num)
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end)
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end
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def evaluate(command), do: evaluate(command, nil, 0)
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def evaluate([], nil, acc), do: acc
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def evaluate([:multiply | rest], nil, acc), do: evaluate(rest, :multiply, acc)
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def evaluate([:add | rest], nil, acc), do: evaluate(rest, :add, acc)
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def evaluate([:start_group | rest], op, acc) do
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{remaining, group_result} = evaluate(rest, nil, 0)
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evaluate([group_result | remaining], op, acc)
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end
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def evaluate([:end_group | rest], _op, acc), do: {rest, acc}
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def evaluate([num | rest], :multiply, acc), do: evaluate(rest, nil, acc * num)
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def evaluate([num | rest], :add, acc), do: evaluate(rest, nil, acc + num)
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def evaluate([num | rest], nil, 0), do: evaluate(rest, nil, num)
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end
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Day18Part1.run()
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