3 files changed, 94 insertions, 32 deletions

diff --git a/aoc2023-other/day-14/day-14.rkt b/aoc2023-other/day-14/day-14.rkt
new file mode 100644
index 0000000..e90feba
--- /dev/null
+++ b/aoc2023-other/day-14/day-14.rkt
@@ -0,0 +1,43 @@
+#lang racket
+
+(require advent-of-code
+         threading
+         "../../jj-aoc.rkt")
+
+(define input
+  (~> (fetch-aoc-input (find-session) 2023 14 #:cache #true)
+      string-split
+      (map string->list _)
+      transpose))
+
+(define (roll-boulders board)
+  (for/list ([col (in-list board)])
+    (~> col (chunks-by (curry equal? #\#)) (append-map (curryr sort char>?) _))))
+
+(define (score board)
+  (for*/sum ([col (in-list board)] [(row n) (in-indexed (reverse col))] #:when (equal? row #\O))
+            (add1 n)))
+
+;; part 1
+(~> input roll-boulders score)
+
+;; part 2
+(define (rotate-board xss)
+  (~> xss (map reverse _) transpose))
+
+(define (full-cycle board)
+  (foldl (λ (_ acc) (~> acc roll-boulders rotate-board)) board (range 4)))
+
+(define (spin-to-win board)
+  (define cache (make-hash))
+  (define (do-spin board n)
+    (match (hash-ref cache board 'not-found)
+      ['not-found
+       (hash-set! cache board n)
+       (do-spin (full-cycle board) (sub1 n))]
+      [seen
+       (define to-end (modulo n (- seen n)))
+       (score (foldl (λ (_ acc) (full-cycle acc)) board (range to-end)))]))
+  (do-spin board 1000000000))
+
+(~> input spin-to-win)
diff --git a/aoc2023/src/day14/solve.gleam b/aoc2023/src/day14/solve.gleam
index 3113d91..1ad1a18 100644
--- a/aoc2023/src/day14/solve.gleam
+++ b/aoc2023/src/day14/solve.gleam
@@ -1,12 +1,10 @@
 import adglent.{First, Second}
+import gleam/dict
+import gleam/int
 import gleam/io
-import gleam/string
 import gleam/list
 import gleam/order
-import gleam/int
-import gleam/iterator
-import gleam/result
-import utilities/memo.{type Cache}
+import gleam/string
 
 fn parse(input) {
   input
@@ -23,30 +21,22 @@ fn roll_boulders(strs: List(String)) {
   |> list.flatten
 }
 
-fn score(matrix, cache) {
-  use <- memo.memoize(cache, matrix)
-  {
-    use col <- list.map(matrix)
-    list.index_map(list.reverse(col), fn(i, c) { #(i + 1, c) })
-    |> list.fold(
-      0,
-      fn(acc, tup) {
-        case tup {
-          #(n, "O") -> acc + n
-          _ -> acc
-        }
-      },
-    )
+fn score(matrix) {
+  use acc, col <- list.fold(matrix, 0)
+  acc + {
+    use col_acc, char, n <- list.index_fold(list.reverse(col), 0)
+    case char {
+      "O" -> col_acc + n + 1
+      _ -> col_acc
+    }
   }
-  |> int.sum
 }
 
 pub fn part1(input: String) {
-  use cache: Cache(List(List(String)), Int) <- memo.create()
   input
   |> parse
   |> list.map(roll_boulders)
-  |> score(cache)
+  |> score()
   |> string.inspect
 }
 
@@ -56,21 +46,34 @@ fn rotate(matrix) {
   |> list.transpose
 }
 
-fn spin_the_board(matrix, cache) {
-  use <- memo.memoize(cache, matrix)
-  matrix
+fn spin(matrix) {
+  use acc, _ <- list.fold(list.range(1, 4), matrix)
+  acc
   |> list.map(roll_boulders)
   |> rotate
 }
 
+fn spin_cycle(matrix) {
+  let cache = dict.new()
+  check_if_seen(matrix, cache, 1_000_000_000)
+}
+
+fn check_if_seen(matrix, cache, count) {
+  case dict.get(cache, matrix) {
+    Error(Nil) ->
+      check_if_seen(spin(matrix), dict.insert(cache, matrix, count), count - 1)
+    Ok(n) -> {
+      let assert Ok(extra) = int.modulo(count, n - count)
+      list.fold(list.range(1, extra), matrix, fn(acc, _) { spin(acc) })
+      |> score
+    }
+  }
+}
+
 pub fn part2(input: String) {
-  use cache: Cache(List(List(String)), List(List(String))) <- memo.create()
-  use score_cache: Cache(List(List(String)), Int) <- memo.create()
   input
   |> parse
-  |> iterator.iterate(spin_the_board(_, cache))
-  |> iterator.map(score(_, score_cache))
-  |> iterator.at(10000)
+  |> spin_cycle
   |> string.inspect
 }
 
diff --git a/jj-aoc.rkt b/jj-aoc.rkt
index 62c1523..4149f2a 100644
--- a/jj-aoc.rkt
+++ b/jj-aoc.rkt
@@ -1,6 +1,22 @@
 #lang racket
 (require advent-of-code)
-(provide open-day)
+(provide open-day
+         transpose
+         chunks-by)
 
 (define (open-day n [year 2021])
-  (open-aoc-input (find-session) year n #:cache (string->path "./cache")))
\ No newline at end of file
+  (open-aoc-input (find-session) year n #:cache (string->path "./cache")))
+
+(define (transpose xss)
+  (apply map list xss))
+
+(define (chunks-by xs [by identity])
+  (define (do-chunks-by xs by group result)
+    (match* (xs group)
+      [('() _) (reverse (cons group result))]
+      [((list* h t) '()) (do-chunks-by t by (cons h group) result)]
+      [((list* h t) (list* g _))
+       #:when (equal? (by h) (by g))
+       (do-chunks-by t by (cons h group) result)]
+      [((list* h t) _) (do-chunks-by t by (list h) (cons group result))]))
+  (do-chunks-by xs by '() '()))