What is the best way to generate all binary strings from a pattern?
Candidates must implement an algorithm to generate all possible binary strings matching a specific pattern containing wildcards. This tests recursion, backtracking, and string manipulation skills.
Why Interviewers Ask This
This problem evaluates a candidate's mastery of recursive backtracking algorithms. Interviewers look for clean code structure and the ability to explore all possibilities systematically. It also checks understanding of base cases and state management during recursion.
How to Answer This Question
Explain the recursive function that processes the pattern character by character. When encountering a wildcard, branch into two recursive calls: one assuming '0' and another assuming '1'. For fixed characters, proceed directly. Define clear base cases where the string is complete. Ensure you discuss time complexity based on the number of wildcards.
Key Points to Cover
- Use recursion to explore all branching paths
- Handle wildcards by creating two branches per occurrence
- Define clear base cases for termination
- Manage the growing string state correctly
Sample Answer
I would use a recursive backtracking approach. The function takes the current pattern index and the partially built string. If the index reaches the length, I print the result. If the current character is '?', I recursiv…
Common Mistakes to Avoid
- Forgetting to backtrack or reset the state after recursive calls
- Incorrectly handling the base case leading to infinite recursion
- Not accounting for patterns with no wildcards
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