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module Day20
open System.IO
open FSharpPlus.Math.Generic
open Common
let mix listWithIds =
let cycle = List.length listWithIds - 1
let move xs idToMove =
let oldIndex = List.findIndex (fst >> (=) idToMove) xs
let element = xs[oldIndex]
let newIndex = int <| remE (int64 oldIndex + snd element) cycle
xs
|> List.removeAt oldIndex
|> List.insertAt newIndex element
seq { 0..cycle } |> Seq.fold move listWithIds
let nthAfterZero n xs =
xs
|> List.item (remE (List.findIndex (snd >> (=) 0L) xs + n) (List.length xs))
|> snd
let groveCoords multiplier rounds input =
let mixed =
input
|> Seq.map (int64 >> (*) multiplier)
|> Seq.indexed
|> List.ofSeq
|> Util.composition rounds mix
nthAfterZero 1000 mixed
+ nthAfterZero 2000 mixed
+ nthAfterZero 3000 mixed
let solution1 = groveCoords 1 1
let solution2 = groveCoords 811589153 10
let test = File.ReadLines("test.txt")
assert (solution1 test = 3)
assert (solution2 test = 1623178306)
let input = File.ReadLines("input.txt")
printfn "%d" <| solution1 input
printfn "%d" <| solution2 input
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