1 files changed, 37 insertions, 0 deletions
diff --git a/AoC2023/day04/solver.lisp b/AoC2023/day04/solver.lisp
new file mode 100644
index 0000000..ec8f09d
--- /dev/null
+++ b/AoC2023/day04/solver.lisp
@@ -0,0 +1,37 @@
+(ql:quickload '(fiveam str transducers))
+
+(defpackage #:day04
+  (:use #:cl #:fiveam)
+  (:local-nicknames (#:t #:transducers)))
+
+(in-package #:day04)
+
+(defparameter eg-input "Card 1: 41 48 83 86 17 | 83 86  6 31 17  9 48 53
+Card 2: 13 32 20 16 61 | 61 30 68 82 17 32 24 19
+Card 3:  1 21 53 59 44 | 69 82 63 72 16 21 14  1
+Card 4: 41 92 73 84 69 | 59 84 76 51 58  5 54 83
+Card 5: 87 83 26 28 32 | 88 30 70 12 93 22 82 36
+Card 6: 31 18 13 56 72 | 74 77 10 23 35 67 36 11")
+
+(defun matching-numbers (line)
+  (destructuring-bind (_card winners haves)
+      (uiop:split-string line :separator '(#\: #\|))
+    (declare (ignorable _card))
+    (intersection
+     (mapcar #'parse-integer
+             (str:split " " winners :omit-nulls t))
+     (mapcar #'parse-integer
+             (str:split " " haves :omit-nulls t)))))
+
+(defun solver1 (lines)
+  (t:transduce
+   (t:comp
+    (t:filter-map #'matching-numbers)
+    (t:map #'length)
+    (t:map (lambda (n) (expt 2 (1- n)))))
+   #'+
+   lines))
+
+(test solutions
+  (is (= 13 (solver1 (uiop:split-string eg-input :separator '(#\Newline)))))
+  (is (= 18619 (solver1 #p"input"))))