AOC_2020_Day8.jl

abstract type Operation end

struct Acc <: Operation
	value::Int
end

struct Jmp <: Operation
	value::Int
end

struct Nop <: Operation
	value::Int
end

function parse_line(data)
	op = data[1:3]
	num = tryparse(Int,data[5:end])
	
	op == "acc" && return Acc(num)
	op == "jmp" && return Jmp(num)
	op == "nop" && return Nop(num)
	
	
end

function parse_data(filename)
	lines = readlines(filename)
	
	tape = Vector{Operation}()
	
	for line in lines
		op = parse_line(line)
		push!(tape,op)
		
	end
	
	return tape
	
end

function excecute(op::Acc,state)
	a = state.accum + op.value
	i = state.index + 1

	return (accum=a,index=i)
end

function excecute(op::Jmp,state)
	a = state.accum
	i = state.index + op.value
	
	return (accum=a,index=i)
	
end

function excecute(op::Nop,state)
	a = state.accum
	i = state.index + 1
	
	return (accum=a,index=i)
end

function d8p1(filename)
	tape = parse_data(filename)
	
	visited = Set{Int}()
	
	state = (accum=0,index=1)
	
	while state.index ∉ visited
		push!(visited,state.index)
		state = excecute(tape[state.index],state)
	end
	
	return state.accum
	
end

d8p1("input_8.txt")

function execute_tape(tape)
	visited = Set{Int}()
	state = (accum=0,index=1)
	
	
	while state.index ∉ visited
		push!(visited,state.index)
		state = excecute(tape[state.index],state)
		
		if state.index == length(tape) + 1
			return (state.accum,true)
		end
		
	end
	
	return (state.accum,false)
end


function d8p2(filename)
	tape = parse_data(filename)
	#println(length(tape))
	
	for index in 1:length(tape)
		
		#println(index)
		typeof(tape[index]) == Acc && continue
		
		new_tape = deepcopy(tape)
		
		if typeof(tape[index]) == Jmp
			new_tape[index] = Nop(tape[index].value)
		elseif typeof(tape[index]) == Nop
			new_tape[index] = Jmp(tape[index].value)
		end
		
		accum,finished = execute_tape(new_tape)
		
		if finished
			return accum
		end
		
	end
	
end

d8p2("input_8.txt")