Day 10 Part 1

README.md

@@ -2,7 +2,7 @@
 
 My (attempted) solutions to [Advent of Code 2020](https://adventofcode.com/2020) in Elixir.
 
-<img width="975" alt="image" src="https://user-images.githubusercontent.com/498229/101621087-a71a8c00-3a58-11eb-9cf5-ca816dbba6ee.png">
+<img width="975" alt="image" src="https://user-images.githubusercontent.com/498229/101746064-b0663000-3b0e-11eb-81bd-92597dba329e.png">
 
 ## Strategy
 

day10/README

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+Day 10 Notes
+
++--------+
+| Part 1 |
++--------+
+
+$ elixir day10part1.exs
+**solved - will add answer after part 2 is complete**
+
+Thoughts:
+
+Noticed that the questions rely on you finding some insight into the data, rather than just
+implementing exactly what the instructions say.
+
+In this case, we just need to sort the data, and compute the difference between all the pairs.
+
+
++-------------------+
+| Part 2 [UNSOLVED] |
++-------------------+
+
+$ elixir day10part2.exs
+...
+
+Thoughts:
+
+So far defeated on this one. I'm obviously missing a fundamental trick.
+
+I went down a massive rabbit hold calculating combinations, which didn't pay off.
+Will leave this for now, and maybe come back to it later.
+
+
++------------------+
+| Overall Thoughts |
++------------------+
+
+Not committing the input for now, in case somebody decides to @ me my answer or something.

day10/day10part1.exs

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+defmodule Day10Part1 do
+  def run do
+    input =
+      File.read!("input")
+      |> String.split("\n", trim: true)
+      |> Enum.map(&String.to_integer/1)
+
+    max = Enum.max(input)
+    outlet = 0
+    built_in = max + 3
+
+    jolts =
+      [outlet, built_in | input]
+      |> Enum.sort()
+      |> Enum.chunk_every(2, 1, :discard)
+      |> Enum.map(fn [a, b] -> b - a end)
+      |> Enum.frequencies()
+
+    IO.puts(jolts[1] * jolts[3])
+  end
+end
+
+Day10Part1.run()