Credit Genie·Software Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say

May 2026

Summary

Technical phone screen for a software engineer role at Credit Genie. The question was a nested loop printing problem that spiraled into a pretty thorough complexity and design discussion. More depth than I expected for what looked like a warmup.

Questions Asked (1)

Implement a function that prints n lines where line i contains integers 1 through i separated by spaces. Then analyze time and auxiliary space complexity for a print-as-you-go approach versus a build-then-print approach, describe common off-by-one pitfalls, and write a version that returns a list of strings instead of printing.

Algorithms & Data StructuresTechnical Trade-offs

Author's notes

Started fine with the basic loop, but the complexity breakdown is where I got a bit tangled.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the problem and edge cases, then implement the print-as-you-go version and analyze its time and space complexity. Next, implement the build-then-print version, compare complexities, and discuss trade-offs. Finally, address off-by-one pitfalls and write a version that returns a list of strings.

Pro tip: Explicitly state that the build-then-print approach uses O(n^2) auxiliary space due to storing all lines, while print-as-you-go uses O(1) auxiliary space (excluding output buffer). This demonstrates awareness of memory trade-offs.

1. Clarify requirements and edge cases

Confirm input constraints (e.g., n >= 0) and expected output format. Discuss handling of n=0 or negative n.

2. Implement print-as-you-go

Write a function that loops i from 1 to n, builds each line by iterating j from 1 to i, and prints it immediately. Analyze time complexity O(n^2) and auxiliary space O(1) (excluding output).

3. Implement build-then-print

Write a function that constructs a list of strings for each line, then prints them all. Analyze time complexity O(n^2) and auxiliary space O(n^2) due to storing all lines.

4. Compare trade-offs

Discuss when to use each approach: print-as-you-go is memory-efficient but not testable; build-then-print allows testing and reuse but uses more memory.

5. Address off-by-one pitfalls and return version

Explain common off-by-one errors (e.g., loops starting at 0 or ending at n-1) and how to avoid them. Then write a function that returns a list of strings instead of printing.

Key Points to Mention

Time complexity: both approaches are O(n^2) because total numbers printed is n(n+1)/2.
Auxiliary space: print-as-you-go uses O(1) extra space (excluding output), build-then-print uses O(n^2) to store all lines.
Off-by-one pitfalls: ensure loops run from 1 to i inclusive, and outer loop from 1 to n inclusive.
Return version: build a list of strings and return it, enabling unit testing and separation of concerns.
Trade-offs: print-as-you-go is memory-efficient but has side effects; build-then-print is testable but memory-heavy.
Edge cases: handle n=0 (print nothing or return empty list) and negative n (throw error or return empty).

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