if the character of s2 is not present in S1 , then check if previous two ASCII characters are present in S1
else if ( mp . ContainsKey ( S2 [ i ] - 1 ) && mp . ContainsKey ( S2 [ i ] - 2 ) ) { mp [ S2 [ i ] - 1 ] = mp [ S2 [ i ] - 1 ] - 1 ; [ S2 [ i ] - 2 ] = mp [ S2 [ i ] - 2 ] - 1 ; } else { return false ; } } return true ; }