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#lang racket
(require advent-of-code
threading
memo)
(struct hand (cards wager))
(define/match (card->int card)
[((? char-numeric?)) (~> card string string->number)]
[(#\A) 14]
[(#\K) 13]
[(#\Q) 12]
[(#\J) 11]
[(#\T) 10]
[(#\*) 1])
(define (parse-hand str #:jokers [jokers? #f])
(match-define (list card-str wager-str) (string-split str))
(define cards
(~> card-str
((λ (str) (if jokers? (string-replace str "J" "*") str)))
string->list
(map card->int _)))
(define wager (~> wager-str string->number))
(hand cards wager))
(define input (~> (open-aoc-input (find-session) 2023 7 #:cache #true) port->lines))
(define/memoize (identify-hand h)
(define freqs (~> h hand-cards (sort <) (group-by identity _) (map length _)))
(match freqs
[(list-no-order 5) 8]
[(list-no-order 1 4) 7]
[(list-no-order 2 3) 6]
[(list-no-order 1 1 3) 5]
[(list-no-order 1 2 2) 4]
[(list-no-order 1 1 1 2) 3]
[(list-no-order 1 1 1 1 1) 2]
[_ 1]))
(define (compare-first-card cs1 cs2)
(if (= (first cs1) (first cs2))
(compare-first-card (rest cs1) (rest cs2))
(< (first cs1) (first cs2))))
(define (compare-hands with h1 h2)
(define rank1 (with h1))
(define rank2 (with h2))
(if (= rank1 rank2) (compare-first-card (hand-cards h1) (hand-cards h2)) (< rank1 rank2)))
;; part 1
(define (compare-hands-no-wilds h1 h2)
(compare-hands identify-hand h1 h2))
(define (total-score in #:jokers [jokers? #false])
(define sorted-hands
(~> in
(map (curry parse-hand #:jokers jokers?) _)
(sort (if jokers? compare-hands-no-wilds compare-hands-with-wilds))))
(for/sum ([(h i)
(in-indexed sorted-hands)])
(* (add1 i) (hand-wager h))))
(total-score input)
;; part 2
(define/memoize (find-best-joker-substitution h)
(for/fold ([best-hand (hand '() 0)])
([wild (in-inclusive-range 2 14)])
(define trial-hand
(hand (map (λ (c) (if (= c 1) wild c)) (hand-cards h)) (hand-wager h)))
(if (> (identify-hand trial-hand) (identify-hand best-hand))
trial-hand
best-hand)))
(define (compare-hands-with-wilds h1 h2)
(compare-hands (λ~> find-best-joker-substitution identify-hand) h1 h2))
(total-score input #:jokers #true)
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