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(defvar input (uiop:read-file-string "2-input"))
;; Each newline represents a new round, which we should parse on the go
(defun sensible-convert-input (str)
(cond
((or (string= str "X") (string= str "A")) 0)
((or (string= str "Y") (string= str "B")) 1)
((or (string= str "Z") (string= str "C")) 2)))
;; Round 1
(defvar rounds
(with-input-from-string (stream input)
(loop
for strategy = (read-line stream nil)
until (null strategy)
collect
(let ((opponent (subseq strategy 0 1))
(yours (subseq strategy 2 3)))
(list (sensible-convert-input opponent) (sensible-convert-input yours))))))
(loop
for round in rounds
until (null round)
sum
(destructuring-bind (opp you) round
(+
1 you ;; base score
(cond ; outcome score
((eq you opp) 3)
((eq (mod (+ 1 opp) 3) you) 6)
(t 0)))))
;; Round 2.
;; We can still use the same rounds data as previously, just
;; reinterpret it in when doing the sum.
(defun get-correct-choice (opponent outcome)
(case outcome
(0 (mod (- opponent 1) 3))
(1 opp)
(2 (mod (+ 1 opponent) 3))
(t 0)))
(loop for round in rounds
sum
(destructuring-bind (opp you) round
(let ((choice (get-correct-choice opp you)))
(+ 1 choice
(case you ;; outcome -> score
(0 0)
(1 3)
(2 6)
(t 0))))))
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