This topic is about the Advent of Code 2021 - Day 4 . Thanks to @bjorng , we now have a new Private Leaderboard . The entry code is: 370884-a6a71927

I’m already ashamed by posting this horrible Part 1. At this point, I’ll have to switch to normal function definitions because it’s becoming a spaghetti mess with anons and it’s just Day 4. Don’t ask how I did Part 2, I have to clean both solutions up first. It’s a challenge trying to do this in …

Again, LiveBook: Day 4 Input This time it is a little bit more convoluted, as there are 2 parts of the input. Fortunately we can easily disect the parts via pattern matching. Technically the conversion to the numbers is not needed, but it does no harm and provides additional layer of safety aga…

I’m surprised that you can work out the answers taking diagonals into account. If all numbers in any row or any column of a board are marked, that board wins . (Diagonals don’t count.) By the way, I also checked diagonals until I failed in Part 2. :sweat_smile:

Ah, missed that. This probably is why I needed to spend a little more on Task 2, but in general it doesn’t change the result.

I represented the boards as binaries, << 22, 13, 17, 11, 0, 8, 2, 23, 4, 24, 21, 9, 14, 16, 7, 6, 10, 3, 18, 5, 1, 12, 20, 15, 19 >> where marked number becomes <<-1::signed>> defp mark_board(board, number) do String.replace(board, <<number>>, <<-1>>, global: false) end and used …

My solution I created a struct that contained a reverse index {value -> {row, col}}, the sum of the fields, and the amount of unfinished columns and rows defmodule Board do defstruct [:index, :row_count, :column_count, :sum, :winner] def new(matrix) # Returns the updated board, marking it as…

Wow, that was a whole lot of fun reading your solutions! I learned new ways of metaprogramming from your code. :heart:

My Liveview solution here: https://github.com/stefanluptak/advent-of-code/blob/main/day_04.livemd Surprisingly, this day puzzle was a lot more pleasant for me compared to the Day 03 (esp part 2). That frustrated me a lot. :smiley:

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Advent of Code 2021 - Day 4

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michallepicki December 4, 2021, 11:44am 16

You got lucky! Every user’s input is different and many people got stuck there