124 lines
4.1 KiB
Elixir
124 lines
4.1 KiB
Elixir
defmodule AOC.Prelude do
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@moduledoc """
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Commonly used functions
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"""
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@doc """
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Splits a String input into lists of lines.
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Excludes any leading or trailing lines from the output list.
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"""
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@spec lines(String.t()) :: [String.t()]
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def lines(str) do
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String.split(str, "\n", trim: true)
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end
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@doc """
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Takes a string containing multiple integers and returns a list of the parsed
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integers.
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The input is split on the given seperator. A single space is used if none is
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provided.
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"""
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@spec ints(String.t()) :: [integer()]
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@spec ints(String.t(), separator :: String.t()) :: [integer()]
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def ints(str, separator \\ " ") do
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str
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|> String.split(separator, trim: true)
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|> Enum.map(&String.to_integer/1)
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end
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@type coord() :: {x :: integer(), y :: integer()}
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@type coord(t) :: {x :: t, y :: t}
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@type map_grid(a) :: %{coord(non_neg_integer()) => a}
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@doc """
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Reads an Advent of Code-style grid of characters into a map of x, y positions
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to a string containing the single character at that position.
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"""
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@spec map_grid(String.t()) :: map_grid(String.t())
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def map_grid(input) do
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for {line, y} <- Enum.with_index(lines(input)), {c, x} <- Enum.with_index(String.graphemes(line)), into: %{} do
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{{x, y}, c}
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end
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end
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@doc """
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Returns `true` if the given position tuple is within the bounds of the
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map_grid.
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"""
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@spec in_bounds?(map_grid(any()), coord()) :: boolean()
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def in_bounds?(grid, pos), do: Map.has_key?(grid, pos)
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@type direction() :: :up | :down | :left | :right | :n | :ne | :e | :se | :s | :sw | :w | :nw
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@doc """
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Applies a single movement to a coordindate pair
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There are also single function shorthands:
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"""
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@spec move_coord(coord(), direction()) :: coord()
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def move_coord({x, y}, dir) when dir in [:up, :n], do: {x, y - 1}
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def move_coord({x, y}, dir) when dir in [:down, :s], do: {x, y + 1}
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def move_coord({x, y}, dir) when dir in [:left, :w], do: {x - 1, y}
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def move_coord({x, y}, dir) when dir in [:right, :e], do: {x + 1, y}
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def move_coord(pos, :ne), do: Enum.reduce([:n, :e], pos, &move_coord/2)
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def move_coord(pos, :se), do: Enum.reduce([:s, :e], pos, &move_coord/2)
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def move_coord(pos, :sw), do: Enum.reduce([:s, :w], pos, &move_coord/2)
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def move_coord(pos, :nw), do: Enum.reduce([:n, :w], pos, &move_coord/2)
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directions = ~w[up down left right n ne e se s sw w nw]a
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for dir <- directions do
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@doc """
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A shorthand for `move_coord(pos, #{inspect(dir)})`
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"""
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@spec unquote(dir)(coord()) :: coord()
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def unquote(dir)(coord), do: move_coord(coord, unquote(dir))
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end
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@type neighborhood_opt() :: {:include_center, boolean()}
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@type neighborhood_opts() :: list(neighborhood_opt())
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@doc """
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For a given coordinate position, returns the [Von Neumann neighborhood][1].
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The Von Neumann neighborhood consists of the cells to the north, south, east,
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and west of the center cell.
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## Options
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- `:include_center`, whether or not to include the passed position. Defaults
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to `false`
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[1]: https://en.wikipedia.org/wiki/Von_Neumann_neighborhood
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"""
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@spec von_neumann_neighborhood(coord()) :: nonempty_list(coord())
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@spec von_neumann_neighborhood(coord(), opts :: neighborhood_opts()) :: nonempty_list(coord())
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def von_neumann_neighborhood(pos, opts \\ []) do
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include_center = Keyword.get(opts, :include_center, false)
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cells = Enum.map(~w[n e s w]a, &move_coord(pos, &1))
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maybe_center = if include_center, do: [pos], else: []
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maybe_center ++ cells
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end
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@doc """
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For a given coordinate position, returns the [Moore neighborhood][1].
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The Moore neighborhood consists of the cells to the north, northeast, east,
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southeast, south, southwest, west, and northwest of the center cell.
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## Options
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- `:include_center`, whether or not to include the passed position. Defaults
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to `false`
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[1]: https://en.wikipedia.org/wiki/Moore_neighborhood
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"""
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def moore_neighborhood(pos, opts \\ []) do
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include_center = Keyword.get(opts, :include_center, false)
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cells = Enum.map(~w[n ne e se s sw w nw]a, &move_coord(pos, &1))
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maybe_center = if include_center, do: [pos], else: []
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maybe_center ++ cells
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end
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end
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