Learn about regex syntax: character classes, quantifiers and more
In this challenge you'll build your own implementation of
grep. Along the way we'll learn about Regex syntax and
how Regexes are evaluated.
In this stage, we'll handle the simplest regex possible: a single character.
a should match "apple", but not "dog".
In this stage, we'll implement support for the
\d matches any digit.
\d should match "1", but not "a".