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34 lines
1.2 KiB
Racket
34 lines
1.2 KiB
Racket
4 years ago
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#lang br
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(require racket/file rackunit racket/sequence racket/set)
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(define toks (for/list ([tok (in-port read (open-input-file "08.rktd"))])
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tok))
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(struct $inst (name val))
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(define instructions (for/vector ([slice (in-slice 2 toks)])
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(apply $inst slice)))
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(define (run insts)
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(let loop ([acc 0][ptr 0][visited null])
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(cond
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[(eq? ptr (vector-length insts)) (cons 'terminated acc)]
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[(memq ptr visited) acc]
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[else
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(define next-visited (cons ptr visited))
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(match (vector-ref insts ptr)
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[($inst 'acc val) (loop (+ acc val) (add1 ptr) next-visited)]
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[($inst 'jmp val) (loop acc (+ ptr val) next-visited)]
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[($inst 'nop val) (loop acc (add1 ptr) next-visited)])])))
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(check-equal? (run instructions) 1818)
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(define (fix-bug insts)
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(for/or ([(inst idx) (in-indexed insts)]
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#:when (memq ($inst-name inst) '(jmp nop)))
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(define new-insts (vector-copy insts))
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(vector-set! insts idx ($inst (if (eq? ($inst-name inst) 'jmp) 'nop 'jmp) ($inst-val inst)))
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(match (run new-insts)
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[(cons 'terminated acc) acc]
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[_ #false])))
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(check-equal? (fix-bug instructions) 187)
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