Duplicate Character Counting in Every Language

Published on 11 October 2020 (Updated: 11 October 2020)

Duplicate Character Counting in Every Language

An overview of the duplicate characters counting problem.

Goal

Although a one line solution for this problem is feasible, just as huge brute force solutions are, we should avoid both of these approaches. Instead, our goal should be to find a fine line between both, where the code is not bogged down but is largely readable and maintainable.

Requirements

The code should return the count of all duplicate, case-insensitive, alphanumeric characters, that occur more than once in the given string. Characters should also be presented in the order in which they appear in the string. For instance, ‘abba’ should output ‘a’ as the firstcharacter that has a duplicate.

Testing

Description Input Output
Basic String “goodbyeblues” Characters: o, Occurrences: 2
Characters: b, Occurrences: 2
Characters: e, Occurrences: 2
Correct Order “abba” Characters: a, Occurrences: 2
Characters: b, Occurrences: 2
Case Distinct “aAbB” No duplicate characters

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