Human Resource Machine/Year 31

Strategy
To perform this task, you must grab every letter from the INBOX, and store the letters in different boxes. When you grab a 0, that's your cue to place the letters in the OUTBOX in the opposite order from how you collected them.

The best way to do this is to use a counter and bump that number up one at a time as you use it to indirectly place the letters in sequential boxes. Then when it's time to put them in the OUTBOX, you decrease the counter by one as you work your way backwards until you're back at the start.

The trick to this is that you'll need to bump the number up once before you even get started. You need to do this because you're not finished until you've copied the last letter (which was initially the first letter you collected), but then you need to reset the count before you start reversing a new string. However, with a slight tweak, this actually allows us to come in under the size requirement while still hitting the speed requirement.

a: b:   BUMPUP   14 INBOX JUMPZ   c    COPYTO   [14] JUMP    b c: d:    BUMPDN   14 JUMPZ   a    COPYFROM [14] OUTBOX JUMP    d

Optimizing
While the above solution already satisfies the speed and size requirement, we can improve the speed even more if we are willing to add one more instruction back in. Instead of preemptively bumping the counter up by one, we will start with box 0, and we'll even copy the contents in box 0 before we finish. We conclude each string by checking the value of box 14 before we bump it down.

a: b:   INBOX JUMPZ   c    COPYTO   [14] BUMPUP  14 JUMP    b c: d:    BUMPDN   14 COPYFROM [14] OUTBOX COPYFROM 14 JUMPZ   a    JUMP     d