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This is a medium difficulty Coding & Algorithms question, commonly asked during Technical Screen rounds at Hopper.

What role is this question designed for?

This question is commonly asked for Software Engineer candidates at Hopper during technical interviews.

How would you sort filenames with numeric segments?

Q: How would you sort filenames with numeric segments?

This question evaluates a candidate's ability to design custom string comparators, parse maximal digit runs and compare numeric values, and handle edge cases such as leading zeros and digit-versus-non-digit ordering.

You are given a list of filename strings (e.g., "file10.txt", "file2.txt", "10file.txt"). Implement a custom sort for these strings using a comparator with the following rules:

Digit-first at the first differing position : When comparing two strings from left to right, if at the first position where they differ one string has a digit ( 0-9 ) and the other has a non-digit, the digit one should come first.
Numeric comparison for digit runs : Treat any maximal consecutive digit substring as a single number and compare by numeric value (so "file10.txt" comes after "file2.txt" ).
Normal character order for non-digit runs : Compare non-digit parts in standard character/lexicographic order.

Return the filenames sorted according to these rules.

Follow-ups:

Leading zeros : How should "file01.txt" and "file1.txt" be ordered if their numeric values are equal? Implement your chosen tie-break rule.
Performance : If there are very many filenames, repeatedly parsing digit runs inside the comparator can be slow. How would you optimize the sorting implementation?

You are given a list of filename strings (e.g., "file10.txt", "file2.txt", "10file.txt"). Implement a custom sort for these strings using a comparator with the following rules:

Digit-first at the first differing position : When comparing two strings from left to right, if at the first position where they differ one string has a digit ( 0-9 ) and the other has a non-digit, the digit one should come first.
Numeric comparison for digit runs : Treat any maximal consecutive digit substring as a single number and compare by numeric value (so "file10.txt" comes after "file2.txt" ).
Normal character order for non-digit runs : Compare non-digit parts in standard character/lexicographic order.

Return the filenames sorted according to these rules.

Follow-ups:

Leading zeros : How should "file01.txt" and "file1.txt" be ordered if their numeric values are equal? Implement your chosen tie-break rule.
Performance : If there are very many filenames, repeatedly parsing digit runs inside the comparator can be slow. How would you optimize the sorting implementation?

How would you sort filenames with numeric segments?

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How would you sort filenames with numeric segments?

Quick Overview

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