text: If previous character is 1 then words that can be formed are K ( 11 ) , L ( 12 ) , M ( 13 ) , N ( 14 ) O ( 15 ) , P ( 16 ) , Q ( 17 ) , R ( 18 ) , S ( 19 )
code: if ( s [ i - 1 ] == '1' ) dp [ i + 1 ] = ( dp [ i + 1 ] + 9 * dp [ i - 1 ] ) % M ;