advent_of_code_2019_05.jl

mutable struct Code
    code::Vector{Int}
    cur::Int
    input::Int
    output::Int
    eop::Bool
end

str2prog(s) = parse.(Int, split(s, ","))

Code(s::String) = Code(str2prog(s), 1, 0, 0, false)

struct Instruction
    op::Int
    modes::Vector{Int}
end

function Instruction(op_code::Int)
    ops = Dict{Int, Int}(
        1 => 3,
        2 => 3,
        3 => 1,
        4 => 1,
        5 => 2,
        6 => 2,
        7 => 3,
        8 => 3,
        99 => 0
    )
    
    op = mod(op_code, 100)
    modes_code = div(op_code, 100)
    modes = zeros(ops[op])
    for i in 1:ops[op]
        modes[i] = mod(modes_code, 10)
        modes_code = div(modes_code, 10)
    end
    
    Instruction(op, modes)
end

Instruction(code::Code) = Instruction(code.code[code.cur])

function apply(code::Code, instruction::Instruction)
    if instruction.op == 99
        code.eop = true
    elseif instruction.op == 1
        a1 = instruction.modes[1] == 1 ? code.code[code.cur + 1] : code.code[code.code[code.cur + 1] + 1]
        a2 = instruction.modes[2] == 1 ? code.code[code.cur + 2] : code.code[code.code[code.cur + 2] + 1]
        code.code[code.code[code.cur + 3] + 1] = a1 + a2
        code.cur += 4
    elseif instruction.op == 2
        a1 = instruction.modes[1] == 1 ? code.code[code.cur + 1] : code.code[code.code[code.cur + 1] + 1]
        a2 = instruction.modes[2] == 1 ? code.code[code.cur + 2] : code.code[code.code[code.cur + 2] + 1]
        code.code[code.code[code.cur + 3] + 1] = a1 * a2
        code.cur += 4
    elseif instruction.op == 3
        code.code[code.code[code.cur + 1] + 1] = code.input
        code.cur += 2
    elseif instruction.op == 4
        code.output = code.code[code.code[code.cur + 1] + 1]
        code.cur += 2
    elseif instruction.op == 5
        a1 = instruction.modes[1] == 1 ? code.code[code.cur + 1] : code.code[code.code[code.cur + 1] + 1]
        a2 = instruction.modes[2] == 1 ? code.code[code.cur + 2] : code.code[code.code[code.cur + 2] + 1]
        if a1 != 0 
            code.cur = a2 + 1 
        else
            code.cur += 3
        end
    elseif instruction.op == 6
        a1 = instruction.modes[1] == 1 ? code.code[code.cur + 1] : code.code[code.code[code.cur + 1] + 1]
        a2 = instruction.modes[2] == 1 ? code.code[code.cur + 2] : code.code[code.code[code.cur + 2] + 1]
        if a1 == 0 
            code.cur = a2 + 1 
        else
            code.cur += 3
        end
    elseif instruction.op == 7
        a1 = instruction.modes[1] == 1 ? code.code[code.cur + 1] : code.code[code.code[code.cur + 1] + 1]
        a2 = instruction.modes[2] == 1 ? code.code[code.cur + 2] : code.code[code.code[code.cur + 2] + 1]
        a3 = code.code[code.cur + 3] + 1
        if a1 < a2
            code.code[a3] = 1
        else
            code.code[a3] = 0
        end
        code.cur += 4
    elseif instruction.op == 8
        a1 = instruction.modes[1] == 1 ? code.code[code.cur + 1] : code.code[code.code[code.cur + 1] + 1]
        a2 = instruction.modes[2] == 1 ? code.code[code.cur + 2] : code.code[code.code[code.cur + 2] + 1]
        a3 = code.code[code.cur + 3] + 1
        if a1 == a2
            code.code[a3] = 1
        else
            code.code[a3] = 0
        end
        code.cur += 4
    end
end

function run(code::Code)
    while !code.eop
        instruction = Instruction(code)
        apply(code, instruction)
    end
end

function run(code::Code, input::Int)
    code.input = input
    run(code)
end

## Some tests

code = Code("3,9,7,9,10,9,4,9,99,-1,8")
run(code, 6)
@assert code.output == 1

code = Code("3,9,7,9,10,9,4,9,99,-1,8")
run(code, 8)
@assert code.output == 0

code = Code("3,12,6,12,15,1,13,14,13,4,13,99,-1,0,1,9")
run(code, 0)
@assert code.output == 0

code = Code("3,12,6,12,15,1,13,14,13,4,13,99,-1,0,1,9")
run(code, 1)
@assert code.output == 1

code = Code("3,12,6,12,15,1,13,14,13,4,13,99,-1,0,1,9")
run(code, -1)
@assert code.output == 1

## Calculation

code = Code(readlines("input.txt")[1])
run(code, 5)
println(code.output)