day 25 complete

1 files changed, 24 insertions, 0 deletions

diff --git a/2022/day-25/day-25.rkt b/2022/day-25/day-25.rkt
new file mode 100644
index 0000000..078cef4
--- /dev/null
+++ b/2022/day-25/day-25.rkt
@@ -0,0 +1,24 @@
+#lang racket
+(require advent-of-code
+         threading)
+
+(define fuel-requirements (port->lines (open-aoc-input (find-session) 2022 25 #:cache #true)))
+
+(define (snafu->decimal snafu)
+  (for/sum ([digit (in-list (~> snafu string->list reverse))] [place (in-naturals)])
+           (define value
+             (match digit
+               [#\= -2]
+               [#\- -1]
+               [c (~> c string string->number)]))
+           (* value (expt 5 place))))
+
+(define (decimal->snafu n [acc '()])
+  (match n
+    [0 (list->string acc)]
+    [n (decimal->snafu (quotient (+ n 2) 5) (cons (string-ref "012=-" (modulo n 5)) acc))]))
+
+;; part 1
+(~> (for/sum ([fuel (in-list fuel-requirements)]) (snafu->decimal fuel)) decimal->snafu)
+
+;; no part 2 メリークリスマス
\ No newline at end of file