Elixir

Total noob, but it’s fun to learn.

{left, right} =
  File.read!("./input.txt")
  |> String.split("\n", trim: true)
  |> Enum.map(fn line ->
    String.split(line)
    |> Enum.map(&String.to_integer/1)
    |> List.to_tuple()
  end)
  |> Enum.unzip()
  |> then(fn {left, right} ->
    {Enum.sort(left), Enum.sort(right)}
  end)

diffs =
  Enum.zip(left, right)
  |> Enum.map(fn {l, r} -> abs(l - r) end)
  |> Enum.sum()

freqs =
  Enum.filter(right, fn r -> r in left end)
  |> Enum.frequencies()

freqsum =
  Enum.map(left, fn n ->
    freq = Map.get(freqs, n, 0)
    n * freq
  end)
  |> Enum.sum()

IO.puts("part 1: #{diffs}")
IO.puts("part 2: #{freqsum}")

It was actually a line break that broke the regex. Changing from a “.” to “[\s\S]” fixed it.

Yes, I guess I held myself to too high expectations. I haven’t even studied CS and learned programming on my own… I’ve been trying to do some exercises and a few courses on algorithms but of course that can’t be compared to going to university. Thanks for the tip, I won’t spend hours in frustration in the coming days for sure. Maybe I should post my attempts even though they are incomplete or fail, to spark discussion.

Ah, yes, that’s it. The lazy solution would be to add a “do()” to the end of the input, right? Haha

Go

package main

import (
	"bufio"
	"fmt"
	"os"
	"sort"
	"strconv"
	"strings"
)

func main() {
	input, _ := os.Open("input.txt")
	defer input.Close()

	left, right := []int{}, []int{}

	scanner := bufio.NewScanner(input)
	for scanner.Scan() {
		line := scanner.Text()
		splitline := strings.Split(line, "   ")
		l, _ := strconv.Atoi(splitline[0])
		r, _ := strconv.Atoi(splitline[1])
		left, right = append(left, l), append(right, r)
	}

	fmt.Printf("part 1 - total diff: %d\n", part1(left, right))
	fmt.Printf("part 2 - new total: %d\n", part2(left, right))
}

func part1(left, right []int) int {
	diff := 0
	sort.Ints(left)
	sort.Ints(right)

	for i, l := range left {
		if l > right[i] {
			diff += (l - right[i])
		} else {
			diff += (right[i] - l)
		}
	}
	return diff
}

func part2(left, right []int) int {
	newTotal := 0

	for _, l := range left {
		matches := 0
		for _, r := range right {
			if l == r {
				matches++
			}
		}
		newTotal += l * matches
	}
	return newTotal
}

Elixir

First time writing Elixir. It’s probably janky af.

I’ve had some help from AI to get some pointers along the way. I’m not competing in any way, just trying to learn and have fun.

~~Part 2 is currently not working, and I can’t figure out why. I’m trying to just remove everything from “don’t()” to “do()” and just pass the rest through the working solution for part 1. Should work, right?

Any pointers?~~

edit; working solution:

defmodule Three do
  def get_input do
    File.read!("./input.txt")
  end

  def extract_operations(input) do
    Regex.scan(~r/mul\((\d{1,3}),(\d{1,3})\)/, input)
    |> Enum.map(fn [_op, num1, num2] ->
      num1 = String.to_integer(num1)
      num2 = String.to_integer(num2)
      [num1 * num2]
    end)
  end

  def sum_products(ops) do
    List.flatten(ops)
    |> Enum.filter(fn x -> is_integer(x) end)
    |> Enum.sum()
  end

  def part1 do
    extract_operations(get_input())
    |> sum_products()
  end

  def part2 do
    String.split(get_input(), ~r/don\'t\(\)[\s\S]*?do\(\)/)
    |> Enum.map(&extract_operations/1)
    |> sum_products()
  end
end

IO.puts("part 1: #{Three.part1()}")
IO.puts("part 2: #{Three.part2()}")

Thanks. I felt very deflated after struggling with something seemingly so simple. I was using Go and couldn’t figure out part 2, at least without nesting loops three layers deep.

Today I decided to try to learn Elixir instead and allowed myself some assistance from Claude.ai, which was much more fun.

I’ve started with Go, but I think I’ve realised AoC isn’t for me. I feel so incredibly dense.

Looking good!

I use Neovim, yes. I’ve actually rotated the trackball about 45° now, feels more natural for the right hand when I shift from the keyboard to it. Needs some adjustments but I think this will be better than with the regular mouse.

It’s really nice being able to scroll by twisting the trackball!

I like it a lot, but as you say it takes a lot of getting used to and practice. I don’t think my WPM is near what it is on a regular keyboard, but we’re talking a few weeks of use versus 30 years of muscle memory … I’m gradually switching over to the Glove. Funnily enough I write better on it when I’m not thinking about it at all.

Yes, or, I’ve had the mouse to the right, too. But I think it makes the most sense in the middle.

The Scylla looks pretty nice too!

Looks like the image has about 90 pixels in it too

2025 is the year of the Linux desktop ergomech keyboard

I actually cast Mage Hand when I need to use it while typing.

Got to spend your money on something, right? I figured it’s a tool I’m using for 8 hours a day to make a living, so it’s worth it to avoid more tendonitis/RSI.

No, this is actually my first split/ergo keyboard. I considered the Moonlander as well, but figured I’d go straight for the endgame, haha. The keywells really work great. My hands are on the larger side though, so I can reach all the keys with ease.

Yep! Having a great time with it.

Wearing sunglasses inside is very cool indeed.