All I am looking for is what data structure i should use to solve a problem like this and why?

when given a set of names with fingerprints will identify groups of names that share a fingerprint.

Input is a sequence of lines:

The line begins with one or more non-whitespace characters.

This sequence of characters is the fingerprint.

The fingerprint is followed by one or more whitespace characters, not including newline.

The name begins with the next non-whitespace character and continues through the next newline.

A name may contain whitespace, but a name never contains a newline.