you should try to like this first take zero length string i.e epsilon ,,than check for length 1 string i.e 0 and 1 ...similarly for length 2 00,01,10,11 and so on....now check whether epsilon gets accepted or not.... in this case yes now for length 1.. i.e 0 and 1 both gets accepted here .....but as you check for 00 i.e length 2 string it does not gets accepted so shortest length which dont gets accepted here is 2
