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{-
--- Day 5: Supply Stacks ---
The expedition can depart as soon as the final supplies have been unloaded from the
ships. Supplies are stored in stacks of marked crates, but because the needed supplies are
buried under many other crates, the crates need to be rearranged.
The ship has a giant cargo crane capable of moving crates between stacks. To ensure none of
the crates get crushed or fall over, the crane operator will rearrange them in a series of
carefully-planned steps. After the crates are rearranged, the desired crates will be at the
top of each stack.
The Elves don't want to interrupt the crane operator during this delicate procedure, but they
forgot to ask her which crate will end up where, and they want to be ready to unload them as
soon as possible so they can embark.
They do, however, have a drawing of the starting stacks of crates and the rearrangement
procedure (your puzzle input). For example:
[D]
[N] [C]
[Z] [M] [P]
1 2 3
move 1 from 2 to 1
move 3 from 1 to 3
move 2 from 2 to 1
move 1 from 1 to 2
In this example, there are three stacks of crates. Stack 1 contains two crates: crate Z is on
the bottom, and crate N is on top. Stack 2 contains three crates; from bottom to top, they are
crates M, C, and D. Finally, stack 3 contains a single crate, P.
Then, the rearrangement procedure is given. In each step of the procedure, a quantity of
crates is moved from one stack to a different stack. In the first step of the above
rearrangement procedure, one crate is moved from stack 2 to stack 1, resulting in this
configuration:
[D]
[N] [C]
[Z] [M] [P]
1 2 3
In the second step, three crates are moved from stack 1 to stack 3. Crates are moved one at a
time, so the first crate to be moved (D) ends up below the second and third crates:
[Z]
[N]
[C] [D]
[M] [P]
1 2 3
Then, both crates are moved from stack 2 to stack 1. Again, because crates are moved one at a
time, crate C ends up below crate M:
[Z]
[N]
[M] [D]
[C] [P]
1 2 3
Finally, one crate is moved from stack 1 to stack 2:
[Z]
[N]
[D]
[C] [M] [P]
1 2 3
The Elves just need to know which crate will end up on top of each stack; in this example, the
top crates are C in stack 1, M in stack 2, and Z in stack 3, so you should combine these
together and give the Elves the message CMZ.
After the rearrangement procedure completes, what crate ends up on top of each stack?
--- Part Two ---
As you watch the crane operator expertly rearrange the crates, you notice the process isn't
following your prediction.
Some mud was covering the writing on the side of the crane, and you quickly wipe it away. The
crane isn't a CrateMover 9000 - it's a CrateMover 9001.
The CrateMover 9001 is notable for many new and exciting features: air conditioning, leather
seats, an extra cup holder, and the ability to pick up and move multiple crates at once.
Again considering the example above, the crates begin in the same configuration:
```
[D]
[N] [C]
[Z] [M] [P]
1 2 3
```
Moving a single crate from stack 2 to stack 1 behaves the same as before:
```
[D]
[N] [C]
[Z] [M] [P]
1 2 3
```
However, the action of moving three crates from stack 1 to stack 3 means that those three moved
crates stay in the same order, resulting in this new configuration:
```
[D]
[N]
[C] [Z]
[M] [P]
1 2 3
```
Next, as both crates are moved from stack 2 to stack 1, they retain their order as well:
```
[D]
[N]
[C] [Z]
[M] [P]
1 2 3
```
Finally, a single crate is still moved from stack 1 to stack 2, but now it's crate C that gets moved:
```
[D]
[N]
[Z]
[M] [C] [P]
1 2 3
```
In this example, the CrateMover 9001 has put the crates in a totally different order: MCD.
Before the rearrangement process finishes, update your simulation so that the Elves know where
they should stand to be ready to unload the final supplies. After the rearrangement procedure
completes, what crate ends up on top of each stack?
-}
{-# LANGUAGE DerivingStrategies #-}
module Main (main) where
import Data.ByteString.Lazy (ByteString)
import Data.Char (digitToInt)
import Options.Applicative (Parser, ParserInfo, argument, execParser, fullDesc, help, helper, info, metavar, str)
import Relude hiding (ByteString, elem, empty, filter, fromList, length, null, optional, readFile, splitAt)
import Text.Parsec (ParseError, parse, (<?>))
import Text.Parsec.ByteString.Lazy (GenParser)
import Text.Parsec.Char (char, digit, string, upper)
import Text.Parsec.Combinator (eof, many1, sepBy1, sepEndBy1)
import Text.Parsec.Prim (parsecMap, try)
type Opts :: Type
newtype Opts = Opts {_filename :: Text} deriving stock (Show)
type Supplies :: Type
newtype Supplies = Supplies {_i :: [[Char]]} deriving stock (Show)
type Order :: Type
data Order = Order {_amount :: Int, _from :: Int, _to :: Int} deriving stock (Show)
parseInput :: FilePath -> ByteString -> Either ParseError (Supplies, [Order])
parseInput = parse $ (,) <$> (supplies <* eol) <*> orders
where
supplies :: GenParser t st Supplies
supplies = Supplies <$> many1 (lineBlock <* eol) <* axis
lineBlock :: GenParser t st [Char]
lineBlock = block `sepBy1` space
block :: GenParser t st Char
block = (char '[' *> upper <* char ']') <|> (' ' <$ try (string " "))
axis :: GenParser t st [()]
axis = void space *> (void int `sepEndBy1` spaces) <* eol
orders :: GenParser t st [Order]
orders = many1 order
order :: GenParser t st Order
order =
Order
<$> (string "move " *> int)
<*> (string " from " *> int)
<*> (string " to " *> int <* (eol <|> eof))
space :: GenParser t st Char
space = char ' '
spaces :: GenParser t st [Char]
spaces = many1 space
int :: GenParser t st Int
int = foldl' (\a i -> a * 10 + digitToInt i) 0 <$> many1 digit
eol :: GenParser t st ()
eol =
parsecMap
(const ())
( try (string "\n\r")
<|> try (string "\r\n")
<|> string "\n"
<|> string "\r"
<?> "end of line"
)
runPart1 :: (Supplies, [Order]) -> (Supplies, [Order])
runPart1 x = x
runPart2 :: (Supplies, [Order]) -> Int
runPart2 = undefined
main :: IO ()
main = do
fileName <- toString . _filename <$> execParser opts
rawInput <- readFileLBS fileName
case parseInput fileName rawInput of
Left e -> do
putTextLn "Error parsing input:"
print e
Right r -> do
print $ runPart1 r
print $ runPart2 r
where
opts :: ParserInfo Opts
opts = info (helper <*> options) fullDesc
options :: Parser Opts
options = Opts <$> filename
filename :: Parser Text
filename = argument str $ metavar "filename" <> help "Input file"
|
