18: Like a GIF For Your Yard

library(mistlecode)

To install `mistlecode` yourself, run `devtools::install_github('guslipkin/mistlecode')`.

 Also loading:  cipheR data.table dplyr purrr slider stringr tidyverse glue

dt <-
  readLines("input.txt") |>
  str_split("") |>
  map(\(x) {
    x |>
      matrix(nrow = 1) |>
      data.frame() 
  }) |>
  bind_rows() |>
  as.matrix()

Part 1

I’ve got a plan this time…

Ugh. I need to find a way to make this faster.

process_light <- function(y, x, m) {
  state <- m[y,x]
  m[y,x] <- ""
  val <- get_adjacent_values(y, x, m)
  if (state == "#") {
    if (sum(val == "#") %in% 2:3) {
      return("#")
    } else {
      return(".")
    }
  } else if (state == ".") {
    if (sum(val == "#") == 3) {
      return("#")
    } else {
      return(".")
    }
  }
}

do_flash <- function(dt, flash, i) {
  while (i > 0) {
    p()
    dt <- 
      expand.grid(
        "y" = seq_len(nrow(dt)),
        "x" = seq_len(ncol(dt))
      ) |>
      furrr::future_pmap_chr(\(y, x) {
        rlang::exec(quote(flash), y, x, dt)
      }) |>
      matrix(nrow = nrow(dt), byrow = FALSE)
    i <- i - 1
  }
  return(dt)
}

future::plan(future::multicore, workers = future::availableCores())

Warning in supportsMulticoreAndRStudio(...): [ONE-TIME WARNING] Forked
processing ('multicore') is not supported when running R from RStudio because
it is considered unstable. For more details, how to control forked processing
or not, and how to silence this warning in future R sessions, see
?parallelly::supportsMulticore

progressr::with_progress({
  i <- 100
  p <- progressr::progressor(steps = i)
  do_flash(dt, process_light, i) |>
    map_int( ~ .x == "#") |>
    sum()
})

[1] 814

future::plan(future::sequential)

Part 2

At least it’s not like 1000 iterations. Just some small changes and a long wait and we’re good to go.

process_light <- function(y, x, m) {
  m[1,1] <- m[nrow(m),1] <- m[1,ncol(m)] <- m[nrow(m), ncol(m)] <- "#"
  state <- m[y,x]
  m[y,x] <- ""
  val <- get_adjacent_values(y, x, m)
  if (state == "#") {
    if (sum(val == "#") %in% 2:3) {
      return("#")
    } else {
      return(".")
    }
  } else if (state == ".") {
    if (sum(val == "#") == 3) {
      return("#")
    } else {
      return(".")
    }
  }
}

do_flash <- function(dt, flash, i) {
  while (i > 0) {
    p()
    dt <- 
      expand.grid(
        "y" = seq_len(nrow(dt)),
        "x" = seq_len(ncol(dt))
      ) |>
      furrr::future_pmap_chr(\(y, x) {
        rlang::exec(quote(flash), y, x, dt)
      }) |>
      matrix(nrow = nrow(dt), byrow = FALSE)
    i <- i - 1
  }
  dt[1,1] <- dt[nrow(dt),1] <- dt[1,ncol(dt)] <- dt[nrow(dt), ncol(dt)] <- "#"
  return(dt)
}

future::plan(future::multicore, workers = future::availableCores())
progressr::with_progress({
  i <- 100
  p <- progressr::progressor(steps = i)
  do_flash(dt, process_light, i) |>
    map_int( ~ .x == "#") |>
    sum()
})

[1] 924

future::plan(future::sequential)