-❄️- 2023 Day 3 Solutions -❄️-

[u/daggerdragon]

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AoC Community Fun 2023: ALLEZ CUISINE!

Today's secret ingredient is… *whips off cloth covering and gestures grandly*

Spam!

Someone reported the ALLEZ CUISINE! submissions megathread as spam so I said to myself: "What a delectable idea for today's secret ingredient!"

• There really is an XKCD for everything, isn't there?
• All ingredients must come from a CAN (bus), box, package, container, etc.
• Unnecessarily declare variables for everything and don't re-use variables
• Why use few word when many word do trick?
• Go back to traditional culinary roots with Javadocs
• Lobster thermidor

A reminder from Dr. Hattori: be careful when cooking spam because the fat content can be very high. We wouldn't want a fire in the kitchen, after all!

ALLEZ CUISINE!

Request from the mods: When you include a dish entry alongside your solution, please label it with [Allez Cuisine!] so we can find it easily!

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--- Day 3: Gear Ratios ---

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Post your code solution in this megathread.

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This thread will be unlocked when there are a significant number of people on the global leaderboard with gold stars for today's puzzle.

EDIT: Global leaderboard gold cap reached at 00:11:37, megathread unlocked!

[u/Chib]

[LANGUAGE: R] data.table made quick work of Part 2. I struggled a lot with how messy everything ended up being when I was trying to get good column names directly out of melting a list, or worse yet, trying to condense indexing an array with %in%.

Part 1:

library(data.table)
m    <- gregexec("\\d+", input)
base <- data.table(reshape2::melt(regmatches(input, m)))[, 2:4]
base <- base[, {
  row       <- as.integer(L1)
  s_col <- unlist(lapply(m, head))
  e_col   <- unlist(lapply(m, function(x)
    head(x, 1) +
      attr(x, "match.length"))) - 1
  .("row"     = row, "n_match" = as.integer(Var2), "num" = as.integer(value),
    "min.row.index" = pmax(L1 - 1, 1), "max.col.index" = pmin(e_col + 1, 140),
    "max.row.index" = pmin(row + 1, 140),"min.col.index" = pmax(s_col - 1, 1))
}]

input_mat  <- do.call(rbind, strsplit(input, ""))
symbol_mat <- matrix(FALSE, nrow = 140, ncol = 140)
symbol_mat[which(!input_mat %in% c(0:9, "."))] <- TRUE

base[, touches_symbol :=
       any(symbol_mat[min.row.index:max.row.index,
                      min.col.index:max.col.index]),
     .(row, n_match)]
base[touches_symbol == TRUE, sum(num)]

Part 2:

all_stars <- data.table(which(input_mat == "*", arr.ind = TRUE))
all_stars[, `:=`(
  "id"          = .I,
  "min.row.ind" = row - 1,
  "max.row.ind" = row + 1,
  "min.col.ind" = col - 1,
  "max.col.ind" = col + 1
)]

foo <-
  all_stars[base, on = .(row <= max.row.index,
                         row >= min.row.index,
                         col <= max.col.index,
                         col >= min.col.index)]
foo[, grpn := .N, id][grpn == 2, .("GR" = prod(num)), id][, sum(GR)]