Left Factoring

Question

How many Minimum number of Backtracks Required :- 

Soln. 

According to me it Max = 3 and Min = 0, because left factoring is there, and say compiler was lucky and chooses the production which finally leads to desired string in one go i.e. S -> aAb -> aab.  So 0 backtracks there isn't it ?

Please Verify if something is wrong?

Comments

Yeah you are right min. will be 0 and max will be 3 because B has two choice so 2 backtracking there ,still we don't get our string but we choose S->aAb, A also have two choice but at second choice we will get our required string so only max 3 backtracking there.