I've seen this problem before so I thought I'd breeze through it.
Clarify the problem constraints (integer operands, operator precedence, no parentheses) and then propose a two-stack or shunting-yard approach to evaluate the expression in a single pass. Walk through an example to demonstrate correctness and discuss time/space complexity.
Pro tip: Handle edge cases like division by zero, negative numbers, and multi-digit operands explicitly, and mention that you'd write unit tests to validate the solution—this shows production-level thinking that Amazon values.
Ask about input format (string, tokens), integer division behavior, operator precedence, and whether parentheses or unary operators are included. Confirm that no eval is allowed.
Select a two-stack approach (one for operands, one for operators) or the shunting-yard algorithm to handle precedence. Explain why this works in O(n) time.
Describe step-by-step how to process tokens: push numbers, compare operator precedence, and apply operators when appropriate. Use a small example like '3+5*2' to illustrate.
Discuss handling division by zero, negative numbers, multi-digit numbers, and invalid expressions. Mention how to return errors gracefully.
State time and space complexity (O(n) time, O(n) space). Suggest test cases to verify correctness, including edge cases.
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