aoc day 5

binary_boarding.rkt

#lang racket

(define input
  (port->lines (open-input-file "input5.in")))

(define (find-row lower upper seq)
  (cond
    [(equal? (string-length seq) 0) lower]
    [(equal? (string-ref seq 0) #\F) (find-row lower (/ (+ lower upper (- 1)) 2) (substring seq 1))]
    [(equal? (string-ref seq 0) #\B) (find-row (/ (+ lower upper 1) 2) upper (substring seq 1))]
    ))

(define (find-col lower upper seq)
  (cond
    [(equal? (string-length seq) 0) lower]
    [(equal? (string-ref seq 0) #\L) (find-col lower (/ (+ lower upper (- 1)) 2) (substring seq 1))]
    [(equal? (string-ref seq 0) #\R) (find-col (/ (+ lower upper 1) 2) upper (substring seq 1))]
    ))

(define (unique-seat-id seq) (+ (* 8 (find-row 0 127 (substring seq 0 7))) (find-col 0 7 (substring seq 7 10))))

(define test_case_1 (equal? (unique-seat-id "FBFBBFFRLR") 357))

(define test_case_2 (equal? (unique-seat-id "BFFFBBFRRR") 567))

(define test_case_3 (equal? (unique-seat-id "FFFBBBFRRR") 119))

(define test_case_4 (equal? (unique-seat-id "BBFFBBFRLL") 820))

; (apply max (map unique-seat-id input)) Part 1 Ans

(define unique-seat-ids (map unique-seat-id input))

(define (bad-neigh-seats unique-seat-ids id)
  (if (and (member (+ id 1) unique-seat-ids) (member (- id 1) unique-seat-ids)) #f #t))

(filter (curry bad-neigh-seats unique-seat-ids ) unique-seat-ids) ; Part 2 Ans