Discussion on: Advent of Code 2020 Solution Megathread - Day 15: Rambunctious Recitation

[Benedict Gaster]

Here is my Haskell solution, please don't ask about performance for that big number :-)

input :: [Int]
input = [16,1,0,18,12,14,19]

tasks :: [Int] -> Int -> Int
tasks input goal = aux (M.fromList $ zip input [1..length input -1], last input) (length input) goal
    where 
        aux (nums, l) size goal 
            | size == goal = l
            | otherwise = let idx = M.findWithDefault size l nums
                          in aux (M.insert l size nums, size-idx) (size+1) goal

main = do
    print (tasks input 2020)
    print (tasks input 30000000)