Created
December 8, 2020 14:41
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import intsets, strutils, strscans, sequtils | |
type | |
Opcode = enum | |
acc = "acc" | |
jmp = "jmp" | |
nop = "nop" | |
Instruction = tuple | |
opcode: Opcode | |
arg: int | |
RunStatus = enum | |
InfiniteLoop, Finished | |
proc parseInstruction(line: string): Instruction = | |
var | |
opcode: string | |
arg: int | |
if scanf(line, "$w $i", opcode, arg): | |
result = (parseEnum[Opcode](opcode), arg) | |
func run(instructions: seq[Instruction]): (RunStatus, int) = | |
var | |
ip = 0 | |
totalAcc = 0 | |
visited: IntSet | |
while true: | |
if visited.contains(ip): | |
return (InfiniteLoop, totalAcc) | |
elif ip >= instructions.len: | |
return (Finished, totalAcc) | |
visited.incl(ip) | |
case instructions[ip].opcode: | |
of acc: | |
totalAcc += instructions[ip].arg | |
ip += 1 | |
of jmp: | |
ip += instructions[ip].arg | |
of nop: | |
ip += 1 | |
var lastMutation = -1 | |
var originalInstructions = toSeq(stdin.lines).map(parseInstruction) | |
while true: | |
var instructions = originalInstructions | |
for i in lastMutation + 1 .. instructions.high: | |
if instructions[i].opcode == nop: | |
instructions[i].opcode = jmp | |
lastMutation = i | |
break | |
elif instructions[i].opcode == jmp: | |
instructions[i].opcode = nop | |
lastMutation = i | |
break | |
let (status, totalAcc) = run(instructions) | |
if status == Finished: | |
echo totalAcc | |
break |
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