I came across an exercise for constructing a PDA for the following language:
$$L = \{ncm \mid n,m\in\{a,b\}^* \text{ and } n \ne m^R\}.$$
Where $L \subseteq ({a,b,c})^*$
So $n$ and $m$ are both a combination of any number of $a$'s and $b$'s, but $n$ is not the reverse of $m$.
Does anyone have some tips or advice, would be much appreciated!