敗中求貝: 線上高中程式解題系統 An Online Judge System For Beginners

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Unknown 提到... @ 2015年10月22日凌晨4:34: 作者已經移除這則留言。
Unknown 提到... @ 2015年10月22日凌晨4:36: 大家好,小弟有幾個問題想麻煩板上高手們替小弟解惑,謝謝
1.Write down the regular expressions for the following languages,and explain your idea:
(a) L={ w | w has no substring "ab"}, ∑ = {a,b}
(b) L={ w | ||w||=3n+2}
(c) L={ w | w contains an even number of a}

2.Prove that the following languages are NOT regular by using closure propertiesand pumping lemma.
Please give formal proofs based on the pumping theory
(a) L={a^nbbba^n}
(b) L={a^nb ,n=k^2 -1}
(c) L={w=w^R}

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