day_4

The general idea is to split the incoming lines into a 2D array of single characters, then we can iterate over sliding windows of 4 characters horizontally, vertically and diagonally and check for “XMAS” ans “SAMX” in these windows, adding to the count.

Part 2 is very similar, only we check each element’s cross value which we first get as a list of list of strings.

(This solution would benefit from using the shared grid module, but I haven’t built that at that time).

Functions

at

</>

pub fn at(data: List(a), index: Int) -> Result(a, Nil)

Gets the entry of a 1D-List at a given index

at_xy

</>

pub fn at_xy(data: List(List(a)), y: Int, x: Int) -> a

Gets the entry at a 2D-List given xy index

check

</>

pub fn check(chars: List(String)) -> Int

count_crosses

</>

pub fn count_crosses(crosses: List(List(String))) -> Int

get_chunks

</>

pub fn get_chunks(
  data: List(List(String)),
  chunk_size: Int,
) -> List(List(List(String)))

Get nxn chunks from a bigger mxm grid

get_crosses

</>

pub fn get_crosses(
  data: List(List(String)),
) -> List(List(String))

Gets all 3-line Crosses from a given grid

get_data

</>

pub fn get_data() -> List(List(String))

get_diagonals

</>

pub fn get_diagonals(
  data: List(List(String)),
) -> List(List(String))

Gets all 4 line diagonals from a given grid

main

</>

pub fn main() -> Nil

part_1

</>

pub fn part_1() -> Int

part_2

</>

pub fn part_2() -> Int