Duplicate Character Counter in Every Language

Welcome to the Duplicate Character Counter page! Here, you’ll find a description of the project as well as a list of sample programs written in various languages.

Description

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-sensitive, 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 first character that has a duplicate.

Testing

Description	Input	Output
No Input		Usage: please provide a string
Empty Input	””	Usage: please provide a string
Basic String	“goodbyeblues”	o: 2 b: 2 e: 2
Correct Order	“abba”	a: 2 b: 2
Case Distinct	“aAbB”	No duplicate characters

Articles

• Duplicate Character Counter in Algol68
• Duplicate Character Counter in C
• Duplicate Character Counter in C++
• Duplicate Character Counter in Java
• Duplicate Character Counter in Mathematica
• Duplicate Character Counter in Python

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