Decode Ways
mediumblind-75dsadpstrings
Asked at
Amazon, Google, LinkedIn, Meta, Microsoft
Problem statement
Implement numDecodings for the classic Decode Ways problem.
This Blind 75 version is framed for frontend interviews: write clean JavaScript, name the invariant out loud, and handle edge cases without over-engineering.
What this tests
- Pattern:
string decoding DP. - Ability to explain time and space complexity clearly.
- Careful handling of empty inputs, duplicates, and boundary cases.
- Production-style JavaScript readability, not just competitive-programming shortcuts.
Requirements & constraints
- Use JavaScript without external libraries.
- Prefer the standard optimal interview approach for this pattern.
- Return deterministic output when multiple valid outputs exist where the prompt implies ordering.
Examples
Example 1
Input: Use the canonical Blind 75 sample for this problem.
Output: Return the value required by the problem statement.
How to approach Decode Ways
The strategy an interviewer expects you to reach for.
Senior Frontend Approach Start by identifying the pattern: string decoding DP. Then define the invariant the loop or recursion maintains before writing code.
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