Discussion on: Advent of Code 2019 Solution Megathread - Day 9: Sensor Boost

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I've been sending input and read output "manually", but it worked well enough for day 7. Interestingly, I learned something about ruby today: arrays are essentially unbounded! so i didn't have worry about the memory issue, I could just read/write to where in the array I wanted and if the array was too short, I'd just read out a nil instead of getting some form of IndexOutOfBoundsError or something.

I made this comment somewhere else in the thread, but the fact that opcode 09 could also work in relative mode, (and that we could write to addresses in relative mode as well) threw me off, I spent way too long trying to track that bug down.

class IntCode
    def initialize(instructions)
        @instructions = instructions
        @ptr = 0
        @in_buff = []
        @out_buff = []
        @rel_base = 0
        @blocked = false
    end

    def send_input(thing)
        @in_buff.push(thing)
    end

    def read_output()
        return @out_buff.shift()
    end

    def inspect()
        puts @instructions.to_s
        puts @out_buff.to_s
    end

    def isBlocked()
        return @blocked
    end

    def read_mem(idx)
        if idx < 0
            puts "wat: negative index"
        end
        val = @instructions[idx]
        if val == nil
            @instructions[idx] = 0
            return 0
        else
            return val
        end
    end

    def write_mem(idx)
    end

    def run()
        @blocked = false
        while @ptr < @instructions.length do
            # puts @ptr, @instructions.to_s
            base_op = read_mem(@ptr)
            # puts base_op
            op = base_op % 100  # get last 2 digits
            flags = base_op / 100 # top n digits
            arg1 = read_value(@instructions, @ptr+1, flags%10)
            if op == 1
                flags = flags / 10
                arg2 = read_value(@instructions, @ptr+2, flags%10)
                flags = flags / 10
                arg3 = read_value(@instructions, @ptr+3, flags%10)
                r = read_mem(arg1) + read_mem(arg2)
                @instructions[arg3] = r
                @ptr += 4
            elsif op == 2
                flags = flags / 10
                arg2 = read_value(@instructions, @ptr+2, flags%10)
                flags = flags / 10
                arg3 = read_value(@instructions, @ptr+3, flags%10)
                r = read_mem(arg1) * read_mem(arg2)
                @instructions[arg3] = r
                @ptr += 4
            elsif op == 3
                if @in_buff.empty?
                    # puts "waiting for input"
                    @blocked = true
                    return false
                end
                input = @in_buff.shift()
                # puts "got input #{input}, putting in location #{arg1}"
                @instructions[arg1] = input.to_i
                @ptr += 2
            elsif op == 4
                output = read_mem(arg1)
                @out_buff.push(output)
                # puts "output: #{output}"
                @ptr += 2
            elsif op == 5
                flags = flags / 10
                arg2 = read_value(@instructions, @ptr+2, flags%10)
                if read_mem(arg1) != 0
                    @ptr = read_mem(arg2)
                else
                    @ptr += 3
                end
            elsif op == 6
                flags = flags / 10
                arg2 = read_value(@instructions, @ptr+2, flags%10)
                if read_mem(arg1) == 0
                    @ptr = read_mem(arg2)
                else
                    @ptr += 3
                end
            elsif op == 7
                flags = flags / 10
                arg2 = read_value(@instructions, @ptr+2, flags%10)
                flags = flags / 10
                arg3 = read_value(@instructions, @ptr+3, flags%10)
                if read_mem(arg1) < read_mem(arg2)
                    @instructions[arg3] = 1
                else
                    @instructions[arg3] = 0
                end
                @ptr += 4
            elsif op == 8
                flags = flags / 10
                arg2 = read_value(@instructions, @ptr+2, flags%10)
                flags = flags / 10
                arg3 = read_value(@instructions, @ptr+3, flags%10)
                if read_mem(arg1) == read_mem(arg2)
                    @instructions[arg3] = 1
                else
                    @instructions[arg3] = 0
                end
                @ptr += 4
            elsif op == 9
                @rel_base += read_mem(arg1)
                # puts "updated relative base to #{@rel_base}"
                @ptr += 2
            elsif op == 99
                # puts "halting!"
                break
            else
                puts "wat"
                return @instructions
            end
        end
        return @instructions
    end

    def read_value(instructions, arg, flag)
        if flag == 1
            return arg
        elsif flag == 2
            v = read_mem(arg) + @rel_base
            return v
        else
            return read_mem(arg)
        end
    end
end


if __FILE__ == $0
    instructions = []
    File.open(ARGV[0], "r") do |file_handle|
        file_handle.each_line do |line|
            instructions = line.split(",").map { |n| n.to_i } 
            break
        end
    end

    vm = IntCode.new(instructions)
    vm.send_input(2)
    vm.run()
    puts vm.read_output()
end