variable A , B , AB for count strings that end with ' A ' but not end with ' B ' , ' B ' but does not end with ' A ' and ' B ' and ends with ' A ' respectively .
int A = 0 , B = 0 , BA = 0 , ans = 0 ; for ( int i = 0 ; i < n ; i ++ ) { String S = s [ i ] ; int L = S . length ( ) ; for ( int j = 0 ; j < L - 1 ; j ++ ) {