-
Notifications
You must be signed in to change notification settings - Fork 0
/
Copy pathday8.rkt
56 lines (52 loc) · 2.41 KB
/
day8.rkt
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
#lang racket
(define (parse-program p)
(list->vector (regexp-match* #rx"([a-z]+) (\\+|\\-)([0-9]+)"
p
#:match-select cdr)))
(define (find-loop prog visited acc pc)
(if (< pc (vector-length prog))
(let ([instr (car (vector-ref prog pc))]
[sign (bytes->string/utf-8 (cadr (vector-ref prog pc)))]
[num (bytes->string/utf-8 (caddr (vector-ref prog pc)))])
(cond [(set-member? visited pc) acc]
[(equal? #"nop" instr)
(find-loop prog (set-add visited pc) acc (+ pc 1))]
[(equal? #"acc" instr)
(find-loop prog (set-add visited pc)
(if (equal? "+" sign)
(+ acc (string->number num))
(- acc (string->number num)))
(+ pc 1))]
[(equal? #"jmp" instr)
(find-loop prog (set-add visited pc) acc
(if (equal? "+" sign)
(+ pc (string->number num))
(- pc (string->number num))))]))
false))
(define (remove-loop prog)
(for ([loc (in-range (vector-length prog))])
(cond [(equal? #"jmp" (car (vector-ref prog loc)))
(begin (vector-set! prog loc (cons #"nop" (cdr (vector-ref prog loc))))
(if (not (find-loop prog (set) 0 0))
(writeln
(find-loop (vector-append prog #((#"jmp" #"+" #"0")))
(set)
0
0))
'())
(vector-set! prog loc (cons #"jmp" (cdr (vector-ref prog loc)))))]
[(equal? #"nop" (car (vector-ref prog loc)))
(begin (vector-set! prog loc (cons #"jmp" (cdr (vector-ref prog loc))))
(if (not (find-loop prog (set) 0 0))
(writeln
(find-loop (vector-append prog #((#"jmp" #"+" #"0")))
(set)
0
0))
'())
(vector-set! prog loc (cons #"nop" (cdr (vector-ref prog loc)))))])))
(call-with-input-file "day8_in.txt"
(lambda (f)
;; Uncomment for part 1
;; (find-loop (parse-program f) (set) 0 0)
(remove-loop (parse-program f))))