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Start by clarifying the scope (e.g., JSON spec version, error handling, performance requirements) and then outline a recursive descent parser that tokenizes the input and builds the data structures. Walk through the grammar rules for each JSON type, discussing how to handle edge cases like nested structures, escapes, and numbers.
Pro tip: Mention that you'd use an index pointer to avoid creating substrings, which improves performance and reduces memory allocation. Also, discuss how you'd handle Unicode escapes and surrogate pairs correctly, as this is a common pitfall.
Ask about the expected JSON features (e.g., support for comments, trailing commas), error handling expectations, and performance requirements. This shows you think about the problem context before coding.
Propose a recursive descent parser with a lexer/tokenizer or a single-pass parser. Explain how you'll handle the grammar and maintain state (e.g., index, current character).
Describe how you'll parse objects, arrays, strings, numbers, booleans, and null. For each, outline the parsing logic and how you'll handle nested structures recursively.
Discuss how you'll detect and report syntax errors (e.g., unexpected tokens, missing commas). Mention handling of escape sequences, Unicode, and number formats.
Explain how you'd test with various JSON inputs, including edge cases. Mention potential optimizations like avoiding string concatenation and using iterative approaches for deep nesting.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.