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Databricks·Software Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say
Apr 2026Remote

Summary

Databricks coding round, got a Snake game design problem which I was not expecting at all. Thought it'd be a straightforward grid traversal thing but the details add up fast.

Questions Asked (1)

Q1

Design and implement a Snake game on a grid of given dimensions. The move(direction) function should advance the snake one step in the given direction and return the current score, or -1 if the snake hits a wall or itself. Food appears at predetermined positions and eating it grows the snake and increments the score.

Algorithms & Data StructuresSystem Design
Author's notes

My first instinct was to just track the head and recompute everything, which would have been a mess.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the game rules and constraints (grid size, food positions, initial snake state, direction handling). Then design the data structures—a deque for the snake body and a set for O(1) collision checks—and implement move(direction) with careful edge-case handling for wall/self-collision and food consumption. Finally, discuss complexity, test cases, and possible extensions like multiple food items or undo.

Pro tip: Explicitly separate game state (snake, food, score) from movement logic, and mention that using a set for the snake body gives O(1) collision checks—this shows you think about performance and clean design, which interviewers at Databricks value.

1. Clarify requirements and constraints

Ask about grid dimensions, initial snake position/length, food placement rules (predetermined list vs. random), direction semantics (absolute vs. relative), and what happens when the snake fills the grid.

2. Choose data structures

Use a deque (or list with head/tail pointers) to represent the snake body for O(1) add/remove at both ends, and a set (or 2D boolean array) for O(1) self-collision checks. Track score and a pointer/index into the food list.

3. Implement move(direction)

Compute the new head position, check wall collision (return -1), check self-collision (return -1 unless the tail is moving away), then update the snake: if food is eaten, grow and increment score; otherwise, remove the tail. Return the current score.

4. Handle edge cases and test

Consider cases like reversing direction (if allowed), snake length 1, food at the new head, and the snake filling the entire grid. Walk through a few moves manually to verify correctness.

5. Analyze complexity and discuss extensions

State that each move is O(1) time and O(n) space for the snake. Mention possible extensions: multiple food items, undo functionality, or rendering the grid.

Key Points to Mention

  • Use a deque for the snake body to achieve O(1) head insertion and tail removal.
  • Use a set (or hash set) for O(1) self-collision detection instead of scanning the body.
  • Carefully handle the case where the new head coincides with the current tail (which is about to move away) to avoid false collision.
  • Maintain a pointer to the next food position in the predetermined list and check for food consumption after moving.
  • Return -1 immediately upon wall or self-collision, and ensure the score is incremented only when food is eaten.
  • Discuss time and space complexity: O(1) per move, O(n) space for the snake.

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