Implement a basic calculator that evaluates a string with +, -, *, /, and parentheses.
Working out arithmetic with precedence and nested parentheses is a parsing task, and a single stack manages both neatly. The traps are operator precedence, multi-digit numbers, and the sign of truncated division. Here is a one-pass solution.
Updated Sep 2026 · Grounded in real GenAI, LLM, and AI/ML engineering interview loops and written to a senior-engineer editorial bar.
Working out arithmetic with precedence and nested parentheses is a parsing task, and a single stack manages both neatly. The traps are operator precedence, multi-digit numbers, and the sign of truncated division. Here is a one-pass solution.
Lead with where the obvious approach breaks, because that is the judgment they are screening for — most candidates jump straight to the happy path and lose the room.
Then walk the failure back through the pipeline in order, naming the one metric the customer's exec sponsor actually cares about before you propose the fix.
