. terminal symbol = a, b, c
. non terminal symbol = E
. rule

E -> aEb
E -> bEa
E -> cE
E -> c
E -> epsilon


a?(bbabb | bbac | cabb | cac | bb | c)*a?


. terminal symbol = a, b
. non terminal symbol
. rule

E -> aEb
E -> bEa
E -> aD
E -> a
D -> aDb
D -> bDa
D -> aD
D -> a
E -> epsilon

(0+ | 0*1+2* | 0*2+ | 1+ | 1*2+ | 2+)