← faire Interview Insights

faire·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Jun 2026

Summary

Faire SWE interview with a Pascal's triangle formatting problem. More of a math-meets-implementation puzzle than a pure algo question, which I wasn't expecting.

Questions Asked (1)

Q1

Given a positive integer representing the height of Pascal's triangle, generate the triangle and print it as centered text. Each number should be right-aligned in a field width equal to the digit count of the largest value in the triangle, and each row should be visually centered relative to the widest row.

Algorithms & Data StructuresTechnical Trade-offs
Author's notes

The actual triangle generation was fine, that part I knew cold.

Create a free account to read the full note

AI HintsAI Generated

Suggested Approach

First, clarify the requirements and edge cases, then outline an algorithm to generate Pascal's triangle row by row. Next, compute the maximum value and its digit count to determine field width, and finally format each row with right-aligned numbers and appropriate centering. Discuss time and space complexity and potential optimizations.

Pro tip: Mention that you can avoid storing the entire triangle by computing each row from the previous one and tracking the maximum value on the fly, which reduces space complexity to O(n) for the current row plus O(1) for the max. Also, note that centering can be achieved by calculating the total width of the widest row and padding each row with spaces on both sides equally.

1. Clarify requirements and edge cases

Ask about input constraints (e.g., maximum height), expected output format (spaces vs tabs), and handling of edge cases like height 0 or 1. Confirm that numbers should be right-aligned and rows centered.

2. Generate Pascal's triangle

Use an iterative approach to build each row from the previous one, starting with [1]. For each new row, compute elements as sums of adjacent elements in the previous row, with 1s at the ends.

3. Determine field width and maximum value

Track the maximum value in the triangle (likely the middle element of the last row) to compute the number of digits, which sets the field width for right-alignment.

4. Format and center each row

For each row, format each number to the field width, join them with spaces, then calculate the total width of the widest row (last row) and pad the current row with leading spaces to center it.

5. Analyze complexity and discuss trade-offs

State time complexity O(n^2) due to generating all elements, and space complexity O(n) if only storing the current row. Discuss alternative approaches like using binomial coefficients or precomputing the entire triangle.

Key Points to Mention

  • Iterative generation using previous row to compute next row
  • Computing maximum value to determine digit width for alignment
  • Centering rows by calculating total width and padding with spaces
  • Time complexity O(n^2) and space complexity O(n) with optimization
  • Handling edge cases such as height 0 or 1
  • Potential optimizations like using binomial coefficients or avoiding full storage

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