Initial commit

2021/day14/day14.scm

@@ -0,0 +1,58 @@
+(import (chicken io)
+	srfi-69
+	srfi-152
+	matchable)
+
+(define (parse-polymer str)
+  (let ((str-lst (string->list str)))
+    (map (lambda (c) (string->symbol (string c))) str-lst)))
+
+(define (parse-rule str)
+  (apply cons (apply cons (map parse-polymer (string-split str " -> ")))))
+
+(define (read-input #!optional (port (current-input-port)))
+  (let ((lines (read-lines port)))
+    (values (parse-polymer (car lines))
+	    (alist->hash-table (map parse-rule (cdr (cdr lines)))))))
+
+(define (template->pairs template)
+  (define h (make-hash-table #:initial 0))
+  (let lp ((polymer template))
+    (match polymer
+      ((a b . rest) (hash-table-update! h (list a b) add1) (lp (cons b rest)))
+      ((a) h)
+      (() h))))
+
+(define (template->counts template)
+  (define h (make-hash-table #:initial 0))
+  (for-each (lambda (c) (hash-table-update! h c add1)) template)
+  h)
+
+(define (polymer-step pairs counts rules)
+  (define new-pairs (make-hash-table #:initial 0))
+  (define new-counts (hash-table-copy counts))
+  (hash-table-for-each
+   pairs
+   (lambda (pair v)
+     (let ((elt (hash-table-ref/default rules pair #f)))
+       (if elt
+	   (begin (hash-table-update! new-pairs (list (car pair) elt) (lambda (x) (+ x v)))
+		  (hash-table-update! new-pairs (list elt (cadr pair)) (lambda (x) (+ x v)))
+		  (hash-table-update! new-counts elt (lambda (x) (+ x v))))
+	   (hash-table-update! new-pairs pair add1)))))
+  (values new-pairs new-counts))
+
+(define (update-polymer pairs counts rules steps)
+  (if (= steps 0)
+      (values pairs counts)
+      (let-values (((new-pairs new-counts) (polymer-step pairs counts rules)))
+	(update-polymer new-pairs new-counts rules (- steps 1)))))
+
+(define (part12 template rules steps)
+  (define-values (pairs counts) (update-polymer (template->pairs template) (template->counts template) rules steps))
+  (let ((vals (hash-table-values counts)))
+    (- (apply max vals) (apply min vals))))
+
+(let-values (((template rules) (read-input)))
+  (print (part12 template rules 10))
+  (print (part12 template rules 40)))

2021/day14/input

@@ -0,0 +1,102 @@
+PFVKOBSHPSPOOOCOOHBP
+
+FV -> C
+CP -> K
+FS -> K
+VF -> N
+HN -> F
+FF -> N
+SS -> K
+VS -> V
+BV -> F
+HC -> K
+BP -> F
+OV -> N
+BF -> V
+VH -> V
+PF -> N
+FC -> S
+CS -> B
+FK -> N
+VK -> H
+FN -> P
+SH -> V
+CV -> K
+HP -> K
+HO -> C
+NO -> V
+CK -> C
+VB -> S
+OC -> N
+NS -> C
+NF -> H
+SF -> N
+NK -> S
+NP -> P
+OO -> S
+NH -> C
+BC -> H
+KS -> H
+PV -> O
+KO -> K
+OK -> H
+OH -> H
+BH -> F
+NB -> B
+FH -> N
+HV -> F
+BN -> S
+ON -> V
+CB -> V
+CF -> H
+FB -> S
+KF -> S
+PS -> P
+OB -> C
+NN -> K
+KV -> C
+BK -> H
+SN -> S
+NC -> H
+PK -> B
+PC -> H
+KN -> S
+VO -> V
+FO -> K
+CH -> B
+PH -> N
+SO -> C
+KH -> S
+HB -> V
+HH -> B
+BB -> H
+SC -> V
+HS -> K
+SP -> V
+KB -> N
+VN -> H
+HK -> H
+KP -> K
+OP -> F
+CO -> B
+VP -> H
+OS -> N
+OF -> H
+KK -> N
+CC -> K
+BS -> C
+VV -> O
+CN -> H
+PB -> P
+BO -> N
+SB -> H
+FP -> F
+SK -> F
+PO -> S
+KC -> H
+VC -> H
+NV -> N
+HF -> B
+PN -> F
+SV -> K
+PP -> K

2021/day14/test

@@ -0,0 +1,18 @@
+NNCB
+
+CH -> B
+HH -> N
+CB -> H
+NH -> C
+HB -> C
+HC -> B
+HN -> C
+NN -> C
+BH -> H
+NC -> B
+NB -> B
+BN -> B
+BB -> N
+BC -> B
+CC -> N
+CN -> C