String and Python Coding Practice | Dataford Interview Questions

A Syapse patient-event label may contain repeated characters. Given a string s, return the first character encountered during a left-to-right scan that has already appeared. If no character repeats, return None.

The result is based on the first repeated occurrence, not the character with the earliest original position. For example, in "abccba", return "c" because the second c is encountered before the second a or b.

Formal Specification

Implement first_repeating_character(s), where s is a string and the return value is either a one-character string or None. Treat uppercase and lowercase letters as different characters, and count spaces and punctuation as valid characters.

Constraints

0 <= len(s) <= 100,000
s may contain Unicode characters, whitespace, and punctuation
Character comparisons are case-sensitive

Function Signature

def first_repeating_character(s):

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Problem

Formal Specification

Constraints

0 <= len(s) <= 100,000
s may contain Unicode characters, whitespace, and punctuation
Character comparisons are case-sensitive

Function Signature

def first_repeating_character(s):

Your question is String and Python Coding Practice. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.