75 lines
2.4 KiB
Nim
75 lines
2.4 KiB
Nim
import streams, strutils, sequtils, sets, options, strformat, tables
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type
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InstructionType = enum nop acc jmp
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Instruction = object
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instruction: InstructionType
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arg: int
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HandheldState = object
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bootcode: seq[Instruction]
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acc: int
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pointer: int
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proc `$`(i: Instruction): string = return fmt"{i.instruction} {i.arg}"
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proc `$`(h: HandheldState): string = return fmt"@{h.pointer} ({h.acc}): {h.bootcode}"
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proc statusString(h: HandheldState): string =
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let i = h.bootcode[h.pointer]
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fmt"{h.pointer}: {i.instruction} {i.arg} ({h.acc})"
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proc newHandheld(bootcode: seq[Instruction], acc = 0, pointer = 0): HandheldState =
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HandheldState(bootcode: bootcode, acc: acc, pointer: pointer)
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proc instructions(s: Stream): seq[Instruction] =
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toSeq(s.lines).mapIt(it.split).mapIt(Instruction(instruction: parseEnum[InstructionType](it[0]), arg: parseInt(it[1].replace("+"))))
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proc stepHandheld(state: var HandheldState): bool =
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if state.pointer >= state.bootcode.len: return true
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let i = state.bootcode[state.pointer]
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case i.instruction:
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of acc: inc state.acc, i.arg
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of jmp: inc state.pointer, i.arg; return false
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else: discard
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inc state.pointer
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proc bootHandheld(h: var HandheldState): bool =
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var hasRun = initHashSet[int]()
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while h.pointer <= h.bootcode.len:
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if h.stepHandheld(): return true
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if hasRun.contains h.pointer: return false
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hasRun.incl h.pointer
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true
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proc part1*(s: Stream): int =
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var h = s.instructions.newHandheld
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if not h.bootHandheld: return h.acc
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proc flipped(h: var HandheldState): HandheldState =
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var nbc = h.bootcode.deepCopy
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case h.bootcode[h.pointer].instruction:
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of nop: nbc[h.pointer].instruction = jmp
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of jmp: nbc[h.pointer].instruction = nop
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else: discard
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nbc.newHandheld
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proc altHandheld(h: var HandheldState): Option[HandheldState] =
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case h.bootcode[h.pointer].instruction:
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of acc: return none(HandheldState)
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of jmp, nop: return some(h.flipped)
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proc part2*(s: Stream): int =
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var alts = initTable[int, HandheldState]()
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var h = s.instructions.newHandheld
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var hasRun = initHashSet[int]()
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while h.pointer <= h.bootcode.len:
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var alt = h.altHandheld
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if alt.isSome: alts[h.pointer] = alt.get
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discard h.stepHandheld()
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if hasRun.contains h.pointer: break
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hasRun.incl h.pointer
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#for i in 1..<alts.len:
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var c = 0
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for k,v in alts.pairs:
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var ah = alts[k]
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if ah.bootHandheld: return ah.acc
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inc c
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