----算24点 穷尽算法
WITH NUM1 AS(

       SELECT DECODE (E.O,
       '+',A.N+B.N,
       '-',A.N-B.N,
       '*',A.N*B.N,
       '/',A.N/B.N
       ) AS N1,C.N N2,D.N N3,'('||A.N||E.O||B.N||')' S
       FROM T24 A,T24 B,T24 C,T24 D ,O24 E
       WHERE A.N NOT IN (B.N,C.N,D.N)
       AND B.N NOT IN (C.N,D.N)
       AND C.N <> D.N),
       -----1111模式
      NUM2 AS( SELECT DECODE(E.O,
       '+',N1+N2,
       '-',N1-N2,
       '*',N1*N2,
       '/',N1/N2
       ) AS M3,N3 M4,'('||S||E.O||N2||')' M5 ,TO_CHAR(N3) M6
        FROM NUM1,O24 E
        UNION ALL---11*11模式
        SELECT DECODE(E.O,
       '+',N3+N2,
       '-',N3-N2,
       '*',N3*N2,
       '/',N3/N2
       ) AS M3,N1 M4,'('||N3||E.O||N2||')' M5,S M6
        FROM NUM1,O24 E),
       
      NUM3 AS(  SELECT DECODE(E.O,
        '+',M3+M4,
        '-1',M3-M4,
        '*',M3*M4,
        '/',M3/M4
        ) AS TOTAL,M5||E.O||M6 TS
         FROM NUM2,O24 E)
         SELECT * FROM NUM3 WHERE TOTAL=24