Set differences and similarities

What this set-operation parsing problem tests

This is a medium-difficulty coding problem that combines string parsing with set arithmetic. It appears frequently in interviews because it requires both careful input handling and correct algorithmic thinking—two skills that separate reliable candidates from careless ones.

The core challenge is parsing a whitespace-tolerant expression while correctly implementing left-to-right evaluation of union and difference operations. You'll need to extract integer lists from bracket notation, apply set operations in order, and return a deduplicated, sorted result. The problem rewards clean separation between the parsing layer (tokenization, bracket matching) and the logic layer (set operations and result formatting).

• String tokenization and bracket-delimited list extraction
• Set union and set difference semantics
• Operator precedence and left-to-right evaluation order
• Handling whitespace robustly without fragile regex
• Output normalization (sorting, deduplication)

Solutions in Python can leverage built-in set types for elegance; C++ solutions benefit from std::set or std::unordered_set and careful iterator or range-based logic. Both languages reward readable parsing over clever one-liners.