Efficient Duplicate Characters Algorithm | Dataford Interview Questions

Given a string, write an efficient algorithm to find all duplicate characters.

Treat uppercase and lowercase characters as distinct, include spaces and punctuation, and return each duplicated character once in its first-occurrence order.

Implement def find_duplicate_characters(s):, returning a list of characters.

Constraints

0 <= len(s) <= 10^5
s may contain letters, digits, whitespace, and punctuation
Character matching is case-sensitive
Return each duplicate character only once

Function Signature

def find_duplicate_characters(s):

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