RegexEditor.dev Logo

Regex Editor & Tester

Build, test, and debug regular expressions

← Back to BlogFormal RE›Classic Problems
← prevnext →
32 / 44
(aaa)*(aaa)* — unary multiples of 3Classic ProblemsFormal RE✨ Emoji Combos

Unary number n = n copies of "a". (aaa)* accepts exactly multiples of 3. The DFA has 3 states tracking n mod 3.

✓ Accepts
εaaaaaaaaaaaaaaaaaa
✗ Rejects
aaaaaaaaaaaa
Loading editor…