My first instinct was a two-pass approach: scan once for the high-precedence ops, then again for the rest.
Clarify the problem constraints, then propose a single-pass solution using a stack to handle operator precedence. Walk through the algorithm with a small example, emphasizing how to manage multi-digit numbers and truncating division. Finally, discuss time and space complexity and potential edge cases.
Pro tip: Mention that you can avoid a stack by maintaining running totals (like a basic calculator) to achieve O(1) extra space, and explicitly handle integer division truncation toward zero (e.g., using Math.trunc in JavaScript or int() in Python).
Ask about input format, operator precedence, division behavior, and whether parentheses or negative numbers are allowed. Confirm that a single pass is required and minimal extra space is desired.
Explain that you'll iterate through the string, building numbers and applying operators. Use a stack to defer addition/subtraction while immediately computing multiplication/division.
Trace the algorithm on a sample expression like '3+2*2' to demonstrate how the stack updates and how precedence is handled.
State that time complexity is O(n) and space is O(n) with a stack, but you can reduce space to O(1) by using running totals. Mention handling of multi-digit numbers and truncating division.
Consider cases like single number, spaces, division by zero (if allowed), and large numbers. Suggest writing unit tests or doing a dry run.
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3/2 was easy, truncation toward zero so 1.
First, clarify the problem context: this appears to be about evaluating arithmetic expressions with operators like +, -, *, /, possibly with precedence. Then, for each input, simulate the evaluation step-by-step, explaining how the parser or evaluator processes tokens, handles operator precedence, and deals with edge cases like trailing operators. Finally, discuss the expected output and the reasoning, including any error handling or assumptions.
Pro tip: Explicitly state your assumptions about the grammar and error handling (e.g., whether trailing operators cause errors or are ignored) before diving into the examples; this shows you think about edge cases and requirements like a senior engineer.
Ask or state what the expression evaluator does: supported operators, precedence rules, associativity, and how errors are handled. Confirm that the inputs are strings to be parsed.
Tokenize into operands 3 and 2 with operator '/'. Apply division, yielding 1.5 (or 1 if integer division). Explain the evaluation order and result.
Tokenize into 14, -, 3, /, 2. Apply operator precedence: division first (3/2 = 1.5), then subtraction (14 - 1.5 = 12.5). If integer division, 3/2 = 1, result 13.
Example: '5+'. Tokenize into 5, +. The parser expects a right operand but finds none. Depending on design, this could throw an error, return 5 (ignoring trailing operator), or produce NaN. Explain the chosen behavior and why.
Compare how different parsing strategies (e.g., shunting-yard, recursive descent) handle these cases. Mention error handling, performance, and robustness considerations.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
Start by clarifying the function's contract and expected behavior, then systematically design test cases covering normal, edge, and invalid inputs. Structure your answer by explaining the test categories, giving concrete examples, and discussing how you would implement and run the tests.
Pro tip: Mention that you prioritize tests based on risk and likelihood of failure, and that you use parameterized tests to reduce duplication while maintaining clarity.
Ask questions to understand the function's purpose, input types, output types, and any documented behavior or constraints. This ensures your tests align with the intended functionality.
Break down test cases into normal (typical valid inputs), edge (boundary values, empty inputs, large inputs), and invalid (wrong types, out-of-range values, null/undefined) categories.
For each category, list concrete examples with expected outputs. For normal cases, include representative valid inputs; for edge cases, include boundaries like zero, max/min values; for invalid inputs, include cases that should throw errors or return specific error indicators.
Describe how you would write the tests using a testing framework (e.g., JUnit, pytest, Jest). Mention use of assertions, setup/teardown, and parameterized tests for efficiency.
Explain how you would run the tests, interpret failures, and maintain them as the function evolves. Emphasize the importance of tests being fast, reliable, and independent.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.