NFA

final = {'C'}
current = {'A'}

delta = {('A','a'):{'A', 'B'},
         ('A','b'):{'A'},
         ('B','b'):{'C'}
         }

string = input("Enter input string: ")
for char in string:
    newcurrent = set()
    for state in current:
        newcurrent |= delta.get((state, char), set())
    current = newcurrent

if any([state in final for state in current]):
    print("string is accepted")
else:
    print("string is rejected")