Bloomberg·Software Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say

Jun 2026

Summary

Bloomberg coding screen, one question, pretty straightforward on the surface but easy to fumble if you're not careful about how you track depth.

Questions Asked (1)

Given a valid string containing parentheses and other characters, find the maximum nesting depth of the parentheses.

Algorithms & Data Structures

Author's notes

Simpler than it looks but I almost overthought it.

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AI HintsAI Generated

Suggested Approach

Clarify that the string is valid (balanced parentheses) and that we only consider parentheses for depth. Then propose a single-pass O(n) time, O(1) space solution using a counter that increments on '(' and decrements on ')', tracking the maximum counter value.

Pro tip: Mention that if the input might be invalid, you can still compute the maximum depth by treating unmatched ')' as depth 0, but since the problem guarantees validity, the simple counter works. Also, note that other characters are ignored.

1. Clarify the problem

Confirm that the string is valid (balanced parentheses) and that only parentheses contribute to nesting depth. Ask if other characters should be ignored.

2. Outline the approach

Explain that you will iterate through the string once, maintaining a current depth counter and a maximum depth variable. Increment on '(', decrement on ')', and update the maximum when incrementing.

3. Walk through an example

Choose a sample string like '(1+(2*3)+((8)/4))+1' and trace the counter and maximum to demonstrate correctness.

4. Analyze complexity

State that the algorithm runs in O(n) time and O(1) extra space, which is optimal since every character must be examined at least once.

5. Handle edge cases

Discuss cases like empty string, no parentheses, or deeply nested parentheses, and confirm the algorithm handles them correctly.

Key Points to Mention

Single-pass iteration with a counter for current depth.
Tracking the maximum depth seen so far.
Ignoring non-parenthesis characters.
O(n) time complexity and O(1) space complexity.
Validity of the string ensures the counter never goes negative.
Edge cases: empty string, no parentheses, maximum nesting at the end.

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