Snapchat·Software Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say

Jun 2026Remote

Summary

Snapchat software engineer interview that was basically one big coding question: build a dynamic list from scratch, no standard library allowed. Straightforward premise but the discussion portion caught me more off guard than the actual coding.

Questions Asked (1)

Implement a dynamic List data structure from scratch using a fixed-size backing array, supporting add, get, set, remove, size, and contains operations, with automatic resizing when the array fills up.

Algorithms & Data StructuresTechnical Trade-offs

Author's notes

The coding part was fine, I got the basic structure down pretty quickly.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the requirements and constraints, then design the class with a fixed-size array and a size variable. Explain the resizing strategy (e.g., doubling) and implement each method with careful index handling and edge cases. Analyze time complexity and discuss trade-offs.

Pro tip: Mention that you'll use System.arraycopy for efficient array copying during resizing, and discuss the amortized O(1) time for add operations. Also, consider using a growth factor like 1.5 or 2 and explain the trade-offs.

1. Clarify requirements and constraints

Ask about expected operations, performance requirements, and whether the list should be generic. Confirm that resizing should be automatic and discuss initial capacity.

2. Design the data structure

Define a class with a generic array (E[]), an int size, and a default initial capacity. Plan the resizing strategy (e.g., double capacity when full).

3. Implement core operations

Write methods for add (append and insert at index), get, set, remove, size, and contains. Handle index bounds and shifting elements for insert/remove.

4. Implement resizing

Create a private resize method that creates a new array with larger capacity, copies elements, and updates the reference. Call it when size equals array length.

5. Analyze and discuss trade-offs

Explain time complexities: O(1) for get/set, O(n) for insert/remove at arbitrary index, amortized O(1) for add at end. Discuss space trade-offs and alternative resizing strategies.

Key Points to Mention

Use of generics to make the list type-safe and reusable.
Resizing strategy: double the capacity when full, using System.arraycopy for efficiency.
Amortized time complexity analysis for add operations.
Handling edge cases: index out of bounds, empty list, resizing when size is 0.
Trade-offs between growth factor (e.g., 1.5 vs 2) and memory/time efficiency.
Consideration of fail-fast iterators or modCount for concurrent modification detection (optional).

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