I'm currently struggling to construct a nondeterministic PDA with an amount of states in $O(n)$ that accepts the following language: $L = \{wcx \, | \, w,x \in \{a,b\}^n \land w \not= x\}$ with c being a delimiter.
In lectures we discussed DPDA that accept $wcw^R$ or NPDA that guess the middle of the word with an $\varepsilon$-transtion and accept $ww^R$.
My idea has been to save $w$ in the stack but then I can't really assure the inequality of $w$ and $x$ then.
