Parsing A Boolean Expression
A hard-tier problem at 70% community acceptance, tagged with String, Stack, Recursion. Reported in interviews at HiLabs and 0 others.
Parsing A Boolean Expression is a hard problem that combines string parsing with stack-based evaluation. You're given a boolean expression string with variables, operators (and, or, not), and nested parentheses, and you need to evaluate it to true or false. It shows up in assessments and requires you to handle operator precedence and recursion correctly. The 70% acceptance rate is deceptive, most solvers who pass did the work to understand the recursion pattern. If this problem hits your live assessment and you blank on how to structure the recursive descent parser, StealthCoder runs invisibly and surfaces a working solution in seconds.
Companies that ask "Parsing A Boolean Expression"
Parsing A Boolean Expression is the kind of problem that decides whether you pass. StealthCoder reads the problem on screen and surfaces a working solution in under 2 seconds. Invisible to screen share. The proctor sees nothing. Built by an engineer who got tired of watching his cohort grind for six months and still get filtered at the OA stage.
Get StealthCoderThe trick is recognizing this as a recursive descent parsing problem, not just a stack simulation. You can't naively push tokens and pop, you need to parse the expression into an abstract syntax tree or evaluate recursively as you parse. The common pitfall is trying to handle all operators with one stack pass. Instead, you parse each operator's arguments recursively, respecting the syntax rules (and and or take comma-separated lists, not takes one argument, and everything's wrapped in parentheses). String manipulation and bracket matching matter less than understanding that recursion lets you delegate to subexpressions. Many candidates try iterative stack approaches and get tangled in state management. The string and recursion topics dominate here. When you're stuck mid-assessment, StealthCoder gives you the recursive template instantly.
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Parsing A Boolean Expression recycles across companies for a reason. It's hard-tier, and most candidates blank under the timer. StealthCoder is the hedge: an AI overlay invisible during screen share. It reads the problem and surfaces a working solution in under 2 seconds. Built by an engineer who got tired of watching his cohort grind for six months and still get filtered at the OA stage. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Parsing A Boolean Expression interview FAQ
Why doesn't a simple stack approach work for this problem?+
Because you don't just evaluate left-to-right. The syntax is nested and operator-specific (and/or take variable-length argument lists; not takes one). A stack alone can't track which subexpression you're parsing. You need recursion to delegate parsing to nested parentheses and arguments.
Is this still asked at real companies?+
Yes. HiLabs reports asking it. The problem is a real interview filter for companies that care about parsing and expression evaluation. It's not a trick question, they want to see clean recursion and string handling.
What's the key insight to not get lost in the recursion?+
Parse one expression at a time. When you see an operator token, recursively parse its arguments (comma-separated, inside parentheses). Base case is a variable (true, false, or a letter). Let recursion handle nesting. Don't try to iterate over the whole string in one pass.
How do String and Stack topics actually show up here?+
String: you're parsing character-by-character, extracting operator names and variable names. Stack: some solutions use a stack to track parentheses or operator contexts, but recursion is cleaner. The stack is optional if you use the call stack instead.
What's the real difficulty, parsing or evaluation?+
Parsing. Once you've built the tree or structured your recursion correctly, evaluation is trivial (evaluate left and right subtrees, apply the operator). The hard part is not getting confused by commas, parentheses, and operator argument counts.
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