Longest Substring Challenge | Dataford Interview Questions

How would you get the biggest (longest) substring from a string?

Asked in the Technical face-to-face stage, early in the technical round alongside project questions. The exact substring criterion was not stated, so use the standard interpretation: return the longest substring containing no repeated characters. If multiple results have the same length, return the one appearing first.

Input and Output

Implement def longest_substring(s):. The input is a string, and the output is the selected substring.

Constraints

0 <= len(s) <= 10^4
The input contains ASCII characters
If multiple longest substrings exist, return the earliest one

Function Signature

def longest_substring(s):

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Problem