Find All Valid Parentheses Combinations
Last updated: October 30, 2025
Quick Overview
Given n pairs of parentheses, generate all combinations of well-formed (valid) parentheses. Return them in any order.
Intuit
October 30, 20259
5
2,118 solved
Given n pairs of parentheses, generate all combinations of well-formed (valid) parentheses. Return them in any order.
A Glider assessment staple. Tests recursive backtracking and understanding of structural constraints. Intuit evaluates how well you prune the search space and write readable recursive code.
What the Interviewer Expects
- Implement using backtracking with open/close count tracking
- Prune invalid branches early rather than generating all permutations and filtering
- Write clean recursive code with clear base case and recursive case
- Analyze time complexity in terms of Catalan numbers
- Handle edge cases like n=0 and n=1
Key Topics to Cover
How to Approach This
- Clarify input constraints and edge cases before writing code.
- Walk through your approach verbally and confirm with the interviewer before coding.
- Start with a brute force solution, then optimize. Mention time and space complexity.
- Test your solution with examples, including edge cases like empty input or duplicates.
- Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
Possible Follow-up Questions
- How would you extend this to generate valid combinations with multiple bracket types?
- Can you implement this iteratively?
- What is the total number of valid combinations for n pairs?
- How would you generate only the k-th valid combination without generating all?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires generating all combinations of valid parentheses given n pairs. This involves recognizing that a valid combination must always have an equal number of open and closed parentheses,...
Approach
- Define the recursive function: Create a function that takes the current string of parentheses, the number of open parentheses used, and the number of closed parentheses used.
- Base case...
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