Zero-prefix numbers

2020/day9/day9.ex

@@ -1,70 +0,0 @@
-defmodule SetTools do
-  def combinations(_, 0) do
-    [[]]
-  end
-
-  def combinations([], _) do
-    []
-  end
-
-  def combinations([head | tail], size) do
-    taken = Stream.map(combinations(tail, size - 1), fn subset -> [head | subset] end)
-    left = combinations(tail, size)
-    Stream.concat(taken, left)
-  end
-end
-
-defmodule Day9 do
-  defp read_input do
-    Path.expand('input', Path.dirname(__ENV__.file))
-    |> File.read!()
-  end
-
-  defp parse_lines(text) do
-    text
-    |> String.trim()
-    |> String.split("\n")
-    |> Enum.map(&String.to_integer/1)
-  end
-
-  def part1 do
-    preamble_size = 25
-
-    read_input()
-    |> parse_lines()
-    |> Stream.chunk_every(preamble_size + 1, 1, :discard)
-    |> Enum.find(fn numbers ->
-      preamble = Enum.take(numbers, preamble_size)
-      next = List.last(numbers)
-
-      has_match =
-        SetTools.combinations(preamble, 2)
-        |> Enum.any?(fn subset -> next == Enum.sum(subset) end)
-
-      !has_match
-    end)
-    |> Enum.at(preamble_size)
-  end
-
-  defp slices(list) do
-    2..(length(list) - 1)
-    |> Stream.flat_map(fn size ->
-      Stream.chunk_every(list, size, 1, :discard)
-    end)
-  end
-
-  def part2 do
-    target = part1()
-
-    ints =
-      read_input()
-      |> parse_lines()
-      |> slices()
-      |> Enum.find(fn slice -> Enum.sum(slice) == target end)
-
-    Enum.min(ints) + Enum.max(ints)
-  end
-end
-
-Day9.part1() |> IO.inspect()
-Day9.part2() |> IO.inspect()