Snapchat·Software Engineer·Take-home Assignment·Intermediate

Intermediate

Jul 2026

Summary

Snapchat SWE interview where they had me build a tappable color-changing grid in iOS, either SwiftUI or UIKit, right there in Xcode. Pretty hands-on, more of a practical coding exercise than a whiteboard thing.

Questions Asked (1)

Build a scrollable grid of squares with a fixed number of rows and columns. Tapping a square should toggle or change that cell's color. Use SwiftUI or UIKit and run it locally in Xcode.

Technical Trade-offsSystem DesignAPI & Integrations

Author's notes

I went with SwiftUI and LazyVGrid because I knew it cold.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements (grid size, scroll direction, color behavior) and then outline a clean architecture using SwiftUI's LazyVGrid or UIKit's UICollectionView. Emphasize performance for large grids and demonstrate a working implementation with toggling logic, explaining trade-offs between the two frameworks.

Pro tip: Mention using a diffable data source or SwiftUI's @State with an array of colors to efficiently update only changed cells, and discuss how this scales for Snapchat's high-performance, interactive UI needs.

1. Clarify Requirements

Ask about grid dimensions, scroll direction, color toggle behavior (e.g., binary toggle or cycle through colors), and whether cells should maintain state. This shows attention to detail and avoids assumptions.

2. Choose Framework and Architecture

Decide between SwiftUI and UIKit based on team familiarity and performance needs. For SwiftUI, use LazyVGrid with a @State array; for UIKit, use UICollectionView with a diffable data source.

3. Implement Grid and Toggling

Create the grid layout, populate cells, and add tap gesture recognizers. Update the cell's color by mutating the data model and refreshing only that cell to maintain performance.

4. Optimize for Performance

Discuss lazy loading, cell reuse, and minimizing state updates. For large grids, consider using a fixed-size array and avoiding full reloads on each tap.

5. Test and Iterate

Run the app in Xcode, test with different grid sizes, and ensure smooth scrolling and immediate color changes. Be prepared to discuss potential improvements like animations or persistence.

Key Points to Mention

Trade-offs between SwiftUI and UIKit for this task (development speed vs. fine-grained control).
Use of LazyVGrid or UICollectionView with diffable data source for efficient updates.
State management: @State in SwiftUI or a data model with notifications in UIKit.
Performance considerations: cell reuse, lazy loading, and avoiding unnecessary redraws.
Handling tap gestures and updating only the affected cell.
Scalability: how the solution would handle a large number of cells (e.g., 100x100).

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