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Airbnb·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Jun 2026

Summary

Airbnb coding screen with one algorithmic visualization problem. Pretty straightforward premise but the implementation details tripped me up more than I expected.

Questions Asked (1)

Q1

Given an array of integers representing terrain heights, print a visual representation of the terrain where each column's height is rendered using '+' characters.

Algorithms & Data Structures
Author's notes

Seemed easy at first, just loop and print some characters.

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AI HintsAI Generated

Suggested Approach

First, clarify the problem constraints and expected output format, then discuss a straightforward approach that iterates from the maximum height down to 1, printing '+' for columns that meet or exceed the current level. Emphasize the time complexity O(maxHeight * n) and consider potential optimizations or alternative representations.

Pro tip: Demonstrate attention to detail by asking about edge cases such as empty arrays, negative heights, or zero heights, and propose how to handle them gracefully. Also, mention that you would write clean, modular code with clear variable names and possibly include a helper function for printing a single row.

1. Clarify requirements and constraints

Ask about input size, height range, expected output format (e.g., spaces for empty columns), and whether the terrain should be printed upside-down or right-side up. Confirm if heights can be zero or negative.

2. Determine the maximum height

Find the maximum value in the array to know how many rows to print. This sets the vertical scale of the visualization.

3. Iterate from top to bottom

For each level from maxHeight down to 1, iterate through the array and print '+' if the column's height is at least the current level, otherwise print a space (or appropriate placeholder).

4. Handle edge cases and output formatting

Address cases like empty array (print nothing or a message), all zeros (print nothing or a flat line), and ensure proper spacing between columns for readability.

5. Analyze complexity and discuss optimizations

State that the time complexity is O(n * maxHeight) and space complexity O(1) extra, then discuss if there's a more efficient way or if the problem expects a different orientation.

Key Points to Mention

  • Time and space complexity analysis: O(n * maxHeight) time, O(1) extra space.
  • Edge cases: empty array, zero heights, negative heights (if allowed), and maximum height.
  • Choice of character for empty spaces (e.g., space vs. '.') and whether to include column separators.
  • Potential alternative: printing the terrain horizontally or using a 2D grid for clarity.
  • Modular code design: separate function for printing a single row or for generating the entire output.
  • Clarifying questions: orientation (top-down vs. bottom-up), expected output format, and constraints.

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