d22 p1

2019/22.rkt

@@ -0,0 +1,55 @@
+#lang br
+(require racket/file rackunit)
+
+(define (stack cards)
+  (reverse cards))
+
+(define (cut n cards)
+  (define-values (head tail)
+    (split-at cards (match n
+                      [(? positive?) n]
+                      [_ (- (length cards) (abs n))])))
+  (append tail head))
+
+(define (increment n cards)
+  (define len (length cards))
+  (define vec (make-vector len))
+  (for ([(card idx) (in-indexed cards)])
+    (vector-set! vec (modulo (* idx n) len) card))
+  (vector->list vec))
+
+(define (run program [deck-size 10])
+  (for/fold ([cards (range deck-size)])
+            ([ln (in-list (string-split program "\n"))])
+    (match (string-split ln)
+      [(list "cut" (app string->number num)) (cut num cards)]
+      [(list _ _ "increment" (app string->number num)) (increment num cards)]
+      [_ (stack cards)])))
+
+(check-equal?
+ (run "deal with increment 7
+deal into new stack
+deal into new stack")
+ '(0 3 6 9 2 5 8 1 4 7))
+
+(check-equal?
+ (run "cut 6
+deal with increment 7
+deal into new stack")
+ '(3 0 7 4 1 8 5 2 9 6))
+
+(check-equal?
+ (run "deal into new stack
+cut -2
+deal with increment 7
+cut 8
+cut -4
+deal with increment 7
+cut 3
+deal with increment 9
+deal with increment 3
+cut -1")
+ '(9 2 5 8 1 4 7 0 3 6))
+
+;; 1
+(check-eq? (index-of (run (file->string "22.rktd") 10007) 2019) 4086)

2019/22.rktd

@@ -0,0 +1,100 @@
+cut -135
+deal with increment 38
+deal into new stack
+deal with increment 29
+cut 120
+deal with increment 30
+deal into new stack
+cut -7198
+deal into new stack
+deal with increment 59
+cut -8217
+deal with increment 75
+cut 4868
+deal with increment 29
+cut 4871
+deal with increment 2
+deal into new stack
+deal with increment 54
+cut 777
+deal with increment 40
+cut -8611
+deal with increment 3
+cut -5726
+deal with increment 57
+deal into new stack
+deal with increment 41
+deal into new stack
+cut -5027
+deal with increment 12
+cut -5883
+deal with increment 45
+cut 9989
+deal with increment 14
+cut 6535
+deal with increment 18
+cut -5544
+deal with increment 29
+deal into new stack
+deal with increment 64
+deal into new stack
+deal with increment 41
+deal into new stack
+deal with increment 6
+cut 4752
+deal with increment 8
+deal into new stack
+deal with increment 26
+cut -6635
+deal with increment 10
+deal into new stack
+cut -3830
+deal with increment 48
+deal into new stack
+deal with increment 39
+cut -4768
+deal with increment 65
+deal into new stack
+cut -5417
+deal with increment 15
+cut -4647
+deal into new stack
+cut -3596
+deal with increment 17
+cut -3771
+deal with increment 50
+cut 1682
+deal into new stack
+deal with increment 20
+deal into new stack
+deal with increment 22
+deal into new stack
+deal with increment 3
+cut 8780
+deal with increment 52
+cut 7478
+deal with increment 9
+cut -8313
+deal into new stack
+cut 742
+deal with increment 19
+cut 9982
+deal into new stack
+deal with increment 68
+cut 9997
+deal with increment 23
+cut -240
+deal with increment 54
+cut -7643
+deal into new stack
+deal with increment 6
+cut -3493
+deal with increment 74
+deal into new stack
+deal with increment 75
+deal into new stack
+deal with increment 40
+cut 596
+deal with increment 6
+cut -4957
+deal into new stack