SIG (Susquehanna)·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

Apr 2026

Summary

SIG had me do a technical phone screen with a pretty focused coding problem. Nothing crazy, but it tests whether you actually know how to work with strings and time arithmetic without reaching for a library.

Questions Asked (1)

Given two time strings in 24-hour 'HH:MM' format where the second time is always later than the first, compute the difference between them in minutes.

Algorithms & Data StructuresTechnical Trade-offs

Author's notes

Straightforward on the surface but they wanted you to walk through every step out loud.

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AI HintsAI Generated

Suggested Approach

Convert both times to total minutes since midnight by parsing hours and minutes, then subtract the earlier from the later. This avoids complex date/time libraries and edge cases, and clearly handles the given constraints.

Pro tip: Mention that you assume the second time is always later, so no need to handle negative differences or day rollover; this shows you read the problem carefully and can simplify based on constraints.

1. Clarify input format and constraints

Confirm that times are in 'HH:MM' 24-hour format, with hours 00-23 and minutes 00-59, and that the second time is always later. This ensures no edge cases like negative differences.

2. Parse time strings into components

Split each string by ':' to extract hours and minutes as integers. For example, '14:30' becomes hours=14, minutes=30.

3. Convert to total minutes since midnight

Compute total minutes for each time as hours * 60 + minutes. This normalizes both times to a single integer scale.

4. Compute the difference

Subtract the earlier total minutes from the later total minutes to get the difference in minutes. Since the second time is later, the result is non-negative.

5. Return the result

Output the integer difference. Optionally, discuss how you would handle invalid inputs or extend to multiple days if needed.

Key Points to Mention

Time complexity is O(1) since parsing and arithmetic are constant time operations.
Space complexity is O(1) as only a few integer variables are used.
Edge cases: same hour but different minutes, midnight (00:00) as start, and times like 23:59 to 00:00 (though not needed here due to constraint).
Alternative approaches: using language-specific date/time libraries, but manual conversion is simpler and more efficient.
Trade-offs: manual parsing is straightforward but may lack validation; using libraries adds overhead but handles more formats.
Test cases: e.g., '01:00' to '02:30' gives 90 minutes; '00:00' to '23:59' gives 1439 minutes.

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