| 1 | (asdf:load-system :adventofcode2020) |
| 2 | (in-package #:adventofcode2020) |
| 3 | |
| 4 | (defun calc-seat (seat-spec) |
| 5 | (let ((row (string-right-trim "RL" seat-spec)) |
| 6 | (col (string-left-trim "FB" seat-spec)) |
| 7 | (convert-to-int |
| 8 | (lambda (str one) |
| 9 | (loop with len = (1- (length str)) |
| 10 | for c across str |
| 11 | for i downfrom len |
| 12 | summing (if (char= c one) |
| 13 | (ash 1 i) 0))))) |
| 14 | (mapcar convert-to-int (list row col) '(#\B #\R)))) |
| 15 | |
| 16 | (defun calc-seat-id (row-col) |
| 17 | (destructuring-bind (row col) row-col |
| 18 | (+ (* row 8) col))) |
| 19 | |
| 20 | (day 05 input |
| 21 | (let* ((lines (list-from input)) |
| 22 | (seat-ids (-<>> lines |
| 23 | (mapcar (compose #'calc-seat-id #'calc-seat)) |
| 24 | (sort <> #'>)))) |
| 25 | (part1 (first seat-ids)) |
| 26 | (part2 (loop for big in seat-ids |
| 27 | for small in (cdr seat-ids) |
| 28 | when (= small (- big 2)) |
| 29 | return (1+ small))))) |
| 30 | |
| 31 | (def-suite day05) |
| 32 | (in-suite day05) |
| 33 | |
| 34 | (test calc-seats |
| 35 | (is (equal |
| 36 | '((44 5) (70 7) (14 7) (102 4)) |
| 37 | (mapcar #'calc-seat '("FBFBBFFRLR" "BFFFBBFRRR" |
| 38 | "FFFBBBFRRR" "BBFFBBFRLL"))))) |
| 39 | |
| 40 | (run! 'day05) |