2nPDA means 2 way non deterministic push down automata Show that the unary language L = {12* | k > 0} can be recognized by a 2NPDA with only one stack-reversal (i.e., where once it starts popping, it...

2nPDA means 2 way non deterministic push down automata

Extracted text: Show that the unary language L = {12* | k > 0} can be recognized by a 2NPDA with only one stack-reversal (i.e., where once it starts popping, it can no longer push).