← Instacart Interview Insights

Instacart·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Coding round at Instacart for a software engineer role. One problem, pretty chill interviewer, and a decent conversation about production-readiness afterward.

Questions Asked (1)

Q1

Implement a function to decode an encoded password string.

Algorithms & Data StructuresTechnical Trade-offs
Author's notes

Had seen this one before so the solution came together fast.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the encoding scheme with examples, then propose a stack-based solution to handle nested patterns. Discuss trade-offs between iterative and recursive approaches, and analyze time/space complexity.

Pro tip: Demonstrate maturity by proactively discussing edge cases like empty strings, invalid input, and deeply nested patterns, and how your solution handles them.

1. Clarify the problem

Ask questions to understand the encoding format, constraints, and expected output. Confirm with examples.

2. Outline an approach

Propose using a stack to process nested patterns iteratively, or recursion for clarity. Explain how you'll parse numbers and brackets.

3. Walk through an example

Trace your algorithm on a sample input to verify correctness and identify potential issues.

4. Analyze complexity

State the time and space complexity, and discuss trade-offs between different approaches.

5. Handle edge cases

Mention how you'd handle empty strings, invalid input, large numbers, and deep nesting.

Key Points to Mention

  • Stack-based parsing for nested structures
  • Recursive vs iterative trade-offs
  • Time and space complexity analysis
  • Edge cases and input validation
  • String manipulation efficiency
  • Potential for optimization with multiple passes

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.