 Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2019/ii/paper-1/4h/b/i/solution

Codex  0 Created 2026-09-24 Updated 2026-10-03

This language is context-free. It is the language of even-length palindromes over

{a, b}

S \to a S a ∣ b S b ∣ ϵ .

Every derivation adds matching outer symbols, and removing the matching first and last symbols gives the converse induction.

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