day2.rkt

#lang racket
(define (get-input)
  (map string->number (string-split (car (file->lines "day2.txt")) ",")))

(define (add code ip)
  (let ([a (vector-ref code (vector-ref code (+ ip 1)))]
        [b (vector-ref code (vector-ref code (+ ip 2)))])
    (vector-set! code (vector-ref code (+ ip 3)) (+ a b))
    code))

(define (mul code ip)
  (let ([a (vector-ref code (vector-ref code (+ ip 1)))]
        [b (vector-ref code (vector-ref code (+ ip 2)))])
    (vector-set! code (vector-ref code (+ ip 3)) (* a b))
    code))


(define (run-code code noun verb)
  (define (run-op code ip)
    (cond [(= 99 (vector-ref code ip)) code]
          [(= 1 (vector-ref code ip)) (run-op (add code ip) (+ 4 ip))]
          [(= 2 (vector-ref code ip)) (run-op (mul code ip) (+ 4 ip))]))
  (let ([code (list->vector code)])
    (vector-set! code 1 noun)
    (vector-set! code 2 verb)
    (run-op code 0)))

(writeln "Part1: ")
(writeln (vector-ref (run-code (get-input) 12 2) 0))

(define (search code needle)
  (for*/first ([noun (in-range 100)]
               [verb (in-range 100)]
               #:when (= (vector-ref (run-code code noun verb) 0) needle))
    (+ (* 100 noun) verb)))

(writeln "Part2: ")
(writeln (search (get-input) 19690720))