| 1 | (asdf:load-system :adventofcode2020) |
| 2 | (in-package #:adventofcode2020) |
| 3 | |
| 4 | (defun calc-seat (seat-spec) |
| 5 | (loop with len = (1- (length seat-spec)) |
| 6 | for c across seat-spec |
| 7 | for i downfrom len |
| 8 | summing (if (or (char= c #\R) (char= c #\B)) |
| 9 | (ash 1 i) 0))) |
| 10 | |
| 11 | (day 05 input |
| 12 | (let* ((lines (list-from input)) |
| 13 | (seat-ids (-<>> lines |
| 14 | (mapcar #'calc-seat) |
| 15 | (sort <> #'>)))) |
| 16 | (part1 (first seat-ids)) |
| 17 | (part2 (loop for big in seat-ids |
| 18 | for small in (cdr seat-ids) |
| 19 | when (= small (- big 2)) |
| 20 | return (1+ small))))) |
| 21 | |
| 22 | (def-suite day05) |
| 23 | (in-suite day05) |
| 24 | |
| 25 | (test calc-seats |
| 26 | (is (equal |
| 27 | '(357 567 119 820) |
| 28 | (mapcar #'calc-seat '("FBFBBFFRLR" "BFFFBBFRRR" |
| 29 | "FFFBBBFRRR" "BBFFBBFRLL"))))) |
| 30 | |
| 31 | (run! 'day05) |