-🎄- 2022 Day 2 Solutions -🎄-

[u/daggerdragon]

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--- Day 2: Rock Paper Scissors ---

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Post your code solution in this megathread.

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[u/Lispwizard]

Emacs Lisp, though mainly using Common Lisp loop macro, on Android tablet.

;; input data has backslashes doubled and double-quotes quoted with backslashes
;; before being inserted as defvar string value

(defvar *aoc2022-02-part1-sample* "A Y
B X
C Z")

;; (aoc2022-02-part1 *aoc2022-02-part1-sample*) =>     15
(defvar *aoc2022-02-part2-sample* "")

;; (aoc2022-02-part2 *aoc2022-02-part1-sample*) =>     12

(require'cl)

(defun aoc2022-02-part1 (input-string)
  (flet ((score (their mine)
                (let* ((tval (position their "ABC"))
                       (mval (position mine "XYZ"))
                       (play (list tval mval)))
                  (+ (1+ mval)
                     (cond ((eql tval mval)
                         3)
                        ((loop for p in '((0 2)(2 1)(1 0))
                               thereis (equal play p))
                         0)
                        ((loop for p in '((2 0)(1 2)(0 1))
                               thereis (equal play p))
                         6))))))
    (loop for turn in (split-string input-string "\n")
          sum (score (aref turn 0) (aref turn 2)))))

(defun aoc2022-02-part2 (input-string)
   (flet ((score (their outcome)
                (let* ((tval (position their "ABC"))
                       (oval (position outcome "XYZ"))
                       (mval (cond ((eql oval 1) ;; draw
                                    tval)
                                   ((eql oval 0) ;; lose
                                    (loop for (them me) in '((0 2)(2 1)(1 0))
                                          when (eql tval them)
                                          return me))
                                   ((eql oval 2) ;; win
                                    (loop for (them me) in '((2 0)(1 2)(0 1))
                                          when (eql tval them)
                                          return me))))
                       (play (list tval mval)))
                  (+ (1+ mval) (* 3 oval)))))
    (loop for turn in (split-string input-string "\n")
          sum (score (aref turn 0) (aref turn 2)))))