用SQL写的一个24点运算

with  test as (select rownum id, regexp_substr('1,2,3,4', '[^,]+',1,rownum) n from dual connect by rownum < 5)    
select  case when     end_out1=24  then '('||'('||n1||f1||n2||')'||f2||n3||')'||f3||n4||'='||'24'  
             when     end_out2=24  then '('||n1||f1||n2||')'||f3||'('||n3||f2||n4||')'||'='||'24'  
             when     end_out3=24  then n1||f3||'('||'('||n2||f1||n3||')'||f2||n4||')'||'='||'24'  
             end     
                        
from    
     ( select x2.*,d.n n4,f3,   
             decode(f3, '+', c123 + d.n, '-', c123 - d.n, '*', c123 * d.n, '/', c123 / d.n) end_out1,   
             decode(f3, '+', c12 + decode(f2, '+', n3 + d.n, '-', n3 - d.n, '*', n3 * d.n, '/', n3 / d.n),    
                        '-', c12 - decode(f2, '+', n3 + d.n, '-', n3 - d.n, '*', n3 * d.n, '/', n3 / d.n),    
                        '*', c12 * decode(f2, '+', n3 + d.n, '-', n3 - d.n, '*', n3 * d.n, '/', n3 / d.n),    
                        '/', c12 / decode(f2, '+', n3 + d.n, '-', decode(n3,d.n,null,n3-d.n), '*', n3 * d.n, '/', n3 / d.n) ) end_out2,   
             decode(f3, '+', n1 + decode(f2, '+', c23 + d.n, '-', c23 - d.n, '*', c23 * d.n, '/', c23 / d.n),    
                        '-', n1 - decode(f2, '+', c23 + d.n, '-', c23 - d.n, '*', c23 * d.n, '/', c23 / d.n),    
                        '*', n1 * decode(f2, '+', c23 + d.n, '-', c23 - d.n, '*', c23 * d.n, '/', c23 / d.n),    
                        '/', n1 / decode(f2, '+', decode(c23,-1*d.n,null,c23+d.n),    
                                             '-', decode(c23,d.n,null,c23-d.n),    
                                             '*', decode(c23,0,null,c23 * d.n),    
                                             '/', decode(c23,0,null,c23 / d.n) )) end_out3   
      from (select id1,id2,c.id id3,   
                   x1.n1,x1.n2,c.n n3,   
                   f1,f2,x1.c12,   
                   decode(f2, '+', c12+ c.n, '-', c12 - c.n, '*', c12 * c.n, '/', c12 / c.n) c123,   
                   decode(f1, '+', n2+ c.n,'-', n2- c.n, '*', n2* c.n, '/', n2 / c.n) c23   
            from (select a.id id1,b.id id2,   
                         a.n  n1, b.n n2,    
                         f1,    
                         decode(f1, '+', a.n + b.n, '-', a.n - b.n, '*', a.n * b.n, '/', a.n / b.n) c12   
                    from test a,   
                         test b,   
                         (select substr('+-*/', rownum, 1) f1  from dual connect by rownum < 5) x   
                   where a.id <> b.id)            x1,   
                 test c,   
                 (select substr('+-*/', rownum, 1) f2 from dual connect by rownum < 5) x   
            where x1.id1 <> c.id   
             and x1.id2 <> c.id)x2,   
            test d,   
            (select substr('+-*/', rownum, 1) f3 from dual connect by rownum < 5) x   
       where id1<>d.id and   id2<>d.id  and   id3<>d.id ) x3   
where end_out1=24   
    or end_out2=24   
    or end_out3=24