Day 2: Red-Nosed Reports

Mix.install([:kino])

Section

input = Kino.Input.textarea("input")

input = Kino.Input.read(input) |> String.split("\n", trim: true) |> Enum.map(fn item -> 
  String.split(item, " ", trim: true) |> Enum.map(&(String.to_integer(&1)))
end)

Part 1

is_valid? = fn results ->
  in_range = Enum.all?(results, fn(i) -> Kernel.abs(i) in 1..3 end)
  all_inc = Enum.all?(results, fn(i) -> i > 0 end)
  all_dec = Enum.all?(results, fn(i) -> i < 0 end)
  in_range &amp;&amp; (all_inc || all_dec) 
end

for report <- input do
  results = Enum.chunk_every(report, 2, 1, :discard)
  |> Enum.map(fn([left, right]) -> 
      left - right
  end)
  
  if is_valid?.(results), do: 1, else: 0
end |> Enum.sum()

Part 2

is_valid? = fn results ->
  in_range = Enum.all?(results, fn(i) -> Kernel.abs(i) in 1..3 end)
  all_inc = Enum.all?(results, fn(i) -> i > 0 end)
  all_dec = Enum.all?(results, fn(i) -> i < 0 end)
  in_range &amp;&amp; (all_inc || all_dec) 
end

for report <- input do
  Enum.map(0..length(report)-1, fn(drop_item) ->
    trun_report = List.delete_at(report, drop_item)
    results = Enum.chunk_every(trun_report, 2, 1, :discard)
    |> Enum.map(fn([left, right]) -> 
      left - right
    end)
    if is_valid?.(results), do: 1, else: 0
  end)
  |> Enum.any?(&amp;(&amp;1 == 1))
  |> Kernel.if(do: 1, else: 0)
  
end |> Enum.sum()