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(ΣΣ)*(ΣΣ)* — even-length stringsClassic ProblemsFormal RE✨ Emoji Combos

Pairs up characters to enforce even length. L = {w | |w| ≡ 0 mod 2}. 2-state DFA. Generalize to (ΣΣΣ)* for length divisible by 3.

✓ Accepts
εabaaabcdaabb
✗ Rejects
aabcabcdex
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