The multiplication-before-addition part is where people slip up if they just parse left to right.
Start by clarifying the problem constraints and edge cases, then propose a solution using a stack-based approach that processes multiplication before addition. Walk through an example to demonstrate correctness, and discuss time/space complexity and potential trade-offs.
Pro tip: Mention that you can handle the evaluation in a single pass by keeping a running sum and a current term, which avoids using a stack and is more space-efficient. This shows you think about optimization beyond the naive approach.
Ask about input format, allowed operators, handling of spaces, and whether parentheses or negative numbers are needed. Confirm that only positive integers, addition, and multiplication are required.
Decide between stack-based evaluation or a two-pass approach. Explain that multiplication has higher precedence, so it should be evaluated first or handled with a running term.
Write clean code, handling spaces and parsing numbers. Test with examples like '3 + 2 * 2' and edge cases like single number or multiple operators.
State that time complexity is O(n) for string length n, and space complexity is O(1) if using running sum/term, or O(n) if using a stack.
Compare stack-based vs. running sum approaches in terms of readability, space, and extensibility to other operators or parentheses.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.