Solve day04 part2

1 files changed, 31 insertions, 3 deletions

diff --git a/AoC2023/day04/solver.lisp b/AoC2023/day04/solver.lisp
index ec8f09d..2baed03 100644
--- a/AoC2023/day04/solver.lisp
+++ b/AoC2023/day04/solver.lisp
@@ -1,4 +1,4 @@
-(ql:quickload '(fiveam str transducers))
+(ql:quickload '(fiveam str arrows transducers))
 
 (defpackage #:day04
   (:use #:cl #:fiveam)
@@ -28,10 +28,38 @@ Card 6: 31 18 13 56 72 | 74 77 10 23 35 67 36 11")
    (t:comp
     (t:filter-map #'matching-numbers)
     (t:map #'length)
-    (t:map (lambda (n) (expt 2 (1- n)))))
+    (t:map #'1-)
+    (t:map (lambda (n) (expt 2 n))))
    #'+
    lines))
 
+(defun solver1c (lines)
+  (arrows:->>
+   (mapcar #'matching-numbers lines)
+   (remove-if #'null)
+   (mapcar #'length)
+   (mapcar #'1-)
+   (mapcar (lambda (n) (expt 2 n)))
+   (apply #'+)))
+
+(defun solver2 (lines)
+  (let* ((line-count (length lines))
+         (stash (make-hash-table :size line-count)))
+    (loop
+      for line in lines
+      for i from 0
+      for matches = (length (matching-numbers line))
+      do (incf (gethash i stash 0))
+         (dotimes (j matches)
+           (when (< (+ i j 1) line-count)
+             (incf (gethash (+ i j 1) stash 0)
+                   (gethash i stash))))
+      sum (gethash i stash 0))))
+
 (test solutions
   (is (= 13 (solver1 (uiop:split-string eg-input :separator '(#\Newline)))))
-  (is (= 18619 (solver1 #p"input"))))
+  (is (= 13 (solver1c (uiop:split-string eg-input :separator '(#\Newline)))))
+  (is (= 18619 (solver1 #p"input")))
+  (is (= 18619 (solver1c (uiop:read-file-lines "input"))))
+  (is (= 30 (solver2 (uiop:split-string eg-input :separator '(#\Newline)))))
+  (is (= 8063216 (solver2 (uiop:read-file-lines "input")))))