I need an NPDA for the following language if it is context-free, and if it isn't I need a proof using the pumping lemma that it is not a CFL:
$$L_1=\{w_1w_2 \in \{a,b\}^* : |w_1| = |w_2|,w_1\neq w_2\}$$
I need an NPDA for the following language if it is context-free, and if it isn't I need a proof using the pumping lemma that it is not a CFL:
$$L_1=\{w_1w_2 \in \{a,b\}^* : |w_1| = |w_2|,w_1\neq w_2\}$$
$$ S \to aSa | bSb | aXb | bXa $$ $$ X \to aXa | bXb | aXb | bXa | \epsilon $$