71 lines
1.6 KiB
Elixir
71 lines
1.6 KiB
Elixir
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defmodule AOC.Day5 do
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use AOC.Day, day: 5, trim: false
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def parse_input(lines) do
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[init, ops] =
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lines
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|> Enum.chunk_by(&(&1 == "\n"))
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|> Enum.reject(&(&1 == ["\n"]))
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{parse_init(init), parse_ops(ops)}
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end
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def parse_init(init) do
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init
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|> Enum.split(-1)
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|> elem(0)
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|> Enum.map(fn line ->
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line
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|> String.to_charlist()
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|> tl()
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|> Enum.take_every(4)
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end)
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|> Enum.zip_with(&Function.identity/1)
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|> Enum.map(fn stack ->
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Enum.reject(stack, &(&1 == ?\s))
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end)
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end
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def parse_ops(ops) do
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Enum.map(ops, fn op ->
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%{"count" => count, "from" => from, "to" => to} =
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Regex.named_captures(~r/move (?<count>\d+) from (?<from>\d+) to (?<to>\d+)\n/, op)
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%{
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count: String.to_integer(count),
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from: String.to_integer(from) - 1,
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to: String.to_integer(to) - 1
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}
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end)
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end
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def part1(input) do
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move(input, true)
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end
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def part2(input) do
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move(input, false)
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end
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def move({init, ops}, reverse) do
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ops
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|> Enum.reduce(init, fn %{count: count, from: from, to: to}, acc ->
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{acc, removed} = remove(acc, from, count)
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removed = if reverse, do: Enum.reverse(removed), else: removed
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add(acc, to, removed)
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end)
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|> Enum.map(&hd/1)
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end
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def remove(stacks, from, count) do
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{removed, new} = Enum.split(Enum.at(stacks, from), count)
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stacks = List.update_at(stacks, from, fn _ -> new end)
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{stacks, removed}
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end
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def add(stacks, to, removed) do
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added = Enum.concat(removed, Enum.at(stacks, to))
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List.update_at(stacks, to, fn _ -> added end)
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end
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end
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