Instacart VO, two coding rounds (expression eval + shopping cart)

Instacart VO, two coding rounds (expression eval + shopping cart)

Did the Instacart virtual onsite for a backend role last week. Two 60 min coding rounds on CodeSignal, no AI allowed in either, SD is scheduled for next week.

First round was the expression calculation one. You get equations as strings and evaluate them, starts with plain + and -, then parentheses get added, then variables that were defined on earlier lines. I wrote a small tokenizer first and went stack based, which paid off once parentheses showed up. Variables were mostly bookkeeping with a map. Finished every part with maybe 10 min left and we talked about what should happen if a variable is used before it's defined.

Second round was shopping cart checkout. Add items, remove items, get the total, then promotions get layered on top. That part gets messy because the order discounts apply in changes the total, so I asked instead of guessing and he seemed fine with that. Last part was sorting the cart by aisle for the shopper. Couldn't complete. Had the comparator half written when time ran out.

For context I got to the onsite through the full-stack AI OA even though I applied backend, scored low 600s on it.

Does not finishing the last part of round 2 usually sink you at Instacart, or do they weigh the earlier parts more?