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2023/day06.livemd
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       <!-- livebook:{"persist_outputs":true} -->

     

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       # Day 06

     

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       ```elixir

     

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       Mix.install([:kino_aoc])

     

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       ```

     

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       ## Section

     

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       <!-- livebook:{"attrs":{"assign_to":"puzzle_input","day":"6","session_secret":"ADVENT_OF_CODE_SESSION","year":"2023"},"chunks":null,"kind":"Elixir.KinoAOC.HelperCell","livebook_object":"smart_cell"} -->

     

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       ```elixir

     

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       {:ok, puzzle_input} =

     

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         KinoAOC.download_puzzle("2023", "6", System.fetch_env!("LB_ADVENT_OF_CODE_SESSION"))

     

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       ```

     

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       ```

     

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       {:ok, "Time:        44     80     65     72\nDistance:   208   1581   1050   1102"}

     

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       ```

     

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       ```elixir

     

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       # puzzle_input =

     

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       """

     

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       Time:      7  15   30

     

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       Distance:  9  40  200

     

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       """

     

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       |> String.trim()

     

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       ```

     

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       ```

     

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       "Time:      7  15   30\nDistance:  9  40  200"

     

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       ```

     

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       ```elixir

     

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       defmodule Day06 do

     

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         def solve(t, d) do

     

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           delta = t ** 2 - 4 * d

     

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           sq_delta = :math.sqrt(delta)

     

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           diff = if sq_delta == floor(sq_delta), do: 1, else: 0

     

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           x1 = (-t + sq_delta) / -2

     

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           x2 = (-t - sq_delta) / -2

     

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           ceil(x2) - ceil(x1) - diff

     

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         end

     

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       end

     

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       ```

     

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       ```

     

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       {:module, Day06, <<70, 79, 82, 49, 0, 0, 8, ...>>, {:solve, 2}}

     

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       ```

     

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       ## Part 1

     

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       ```elixir

     

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       puzzle_input

     

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       |> String.split("\n")

     

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       |> Enum.map(fn line ->

     

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         line

     

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         |> String.split(" ", trim: true)

     

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         |> tl()

     

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         |> Enum.map(&String.to_integer/1)

     

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       end)

     

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       |> Enum.zip()

     

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       |> Enum.map(fn {t, d} -> Day06.solve(t, d) end)

     

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       |> Enum.product()

     

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       ```

     

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       ```

     

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       32076

     

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       ```

     

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       ## Part 2

     

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       ```elixir

     

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       [t, d] =

     

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         puzzle_input

     

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         |> String.split("\n")

     

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         |> Enum.map(fn line ->

     

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           line

     

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           |> String.split(" ", trim: true)

     

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           |> tl()

     

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           |> Enum.join()

     

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           |> String.to_integer()

     

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         end)

     

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       Day06.solve(t, d)

     

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       ```

     

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       ```

     

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       34278221

     

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       ```

     

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