(asdf:load-system :adventofcode2020)
(in-package #:adventofcode2020)
(named-readtables:in-readtable :adventofcode2020)

(defun count-answers (join ans-list)
  (->> ans-list
    (mapcar λ(map 'list #'identity _))
    (reduce λ(funcall join _0 _1 :test #'char=))
    (length)))

(day 06 input
  (let ((answer-groups (-<>> (list-from input)
                         (split-sequence "" <> :test #'string=)))
        (disjunction (curry #'count-answers #'union))
        (conjunction (curry #'count-answers #'intersection) ))
    (part1 (->> answer-groups (mapcar disjunction) (reduce #'+)))
    (part2 (->> answer-groups (mapcar conjunction) (reduce #'+)))))

(def-suite day06)
(in-suite day06)

(test count-answers-disj
  (is (equal
        '(3 3 3 1 1)
        (mapcar (curry #'count-answers #'union)  
                '(("abc") ("a" "b" "c") ("ab" "ac") 
                          ("a" "a" "a" "a") ("b"))))))

(test count-answers-conj
  (is (equal
        '(3 0 1 1 1)
        (mapcar (curry #'count-answers #'intersection)  
                '(("abc") ("a" "b" "c") ("ab" "ac") 
                          ("a" "a" "a" "a") ("b"))))))

(run! 'day06)