I don’t use elixir much, mainly just learning for some hobby projects I have in mind, but I like doing these puzzles as I learn about functions I don’t use or know much and it’s just a different way of thinking stringing things together in pipelines. I kind of enjoyed the parsing challenge in the second part. Zip and chunk_by are ones I rarely use that helped me out today.
defmodule Puzzle do
def parse_first(input) do
input
|> String.split("\n", trim: true)
|> Enum.map(&String.split(&1, " ", trim: true))
|> Enum.zip()
|> Enum.map(&Tuple.to_list/1)
|> Enum.map(&Enum.reverse/1)
end
def parse_second(input) do
rows = String.split(input, "\n")
operators =
List.last(rows)
|> String.split(" ", trim: true)
rows =
rows
|> List.delete_at(length(rows) - 1)
|> Enum.map(&String.graphemes/1)
|> Enum.zip()
|> Enum.map(&Tuple.to_list/1)
|> Enum.map(&Enum.join/1)
|> Enum.map(&String.trim/1)
|> Enum.chunk_by(&(&1 == ""))
|> Enum.filter(fn chunk -> chunk != [""] end)
Enum.zip(operators, rows)
|> Enum.map(fn {operator, values} -> [operator | values] end)
end
def compute_column([operator | values]) do
case operator do
"*" ->
Enum.reduce(values, 1, fn value_str, acc ->
String.to_integer(value_str) * acc
end)
"+" ->
Enum.reduce(values, 0, fn value_str, acc ->
String.to_integer(value_str) + acc
end)
end
end
end
#Part 1
Puzzle.parse_first(input)
|> Enum.reduce(0, fn col, acc ->
acc + Puzzle.compute_column(col)
end)
#Part 2
Puzzle.parse_second(input)
|> Enum.reduce(0, fn col, acc ->
acc + Puzzle.compute_column(col)
end)
