day06.lisp

   1 (asdf:load-system :adventofcode2020)
   2 (in-package #:adventofcode2020)
   3 (named-readtables:in-readtable :adventofcode2020)
   4
   5 (defun count-answers (join ans-list)
   6   (->> ans-list
   7     (mapcar λ(map 'list #'identity _))
   8     (reduce λ(funcall join _0 _1 :test #'char=))
   9     (length)))
  10
  11 (day 06 input
  12   (let ((answer-groups (-<>> (list-from input)
  13                          (split-sequence "" <> :test #'string=)))
  14         (disjunction (curry #'count-answers #'union))
  15         (conjunction (curry #'count-answers #'intersection) ))
  16     (part1 (->> answer-groups (mapcar disjunction) (reduce #'+)))
  17     (part2 (->> answer-groups (mapcar conjunction) (reduce #'+)))))
  18
  19 (def-suite day06)
  20 (in-suite day06)
  21
  22 (test count-answers-disj
  23   (is (equal
  24         '(3 3 3 1 1)
  25         (mapcar (curry #'count-answers #'union)
  26                 '(("abc") ("a" "b" "c") ("ab" "ac")
  27                           ("a" "a" "a" "a") ("b"))))))
  28
  29 (test count-answers-conj
  30   (is (equal
  31         '(3 0 1 1 1)
  32         (mapcar (curry #'count-answers #'intersection)
  33                 '(("abc") ("a" "b" "c") ("ab" "ac")
  34                           ("a" "a" "a" "a") ("b"))))))
  35
  36 (run! 'day06)