很早以前就想用PLSQL写一个算24点的程序了，后来想了一下没有研究下去，最近上ITPUB的时候正好大家都在讨论，在大牛的基础上修改了一下，基本上思想和算法都是没有变的，就是学习了一下。还有两个大问题没有处理好，一是只用了枚举法，用PLSQL应该可以换个更好的递归算法的；二是没有滤重；反正最后的结果只是最简单的得到答案而已。
具体的可以参见：
http://www.itpub.net/viewthread.php?tid=1061129&extra=page%3D1%26amp%3Bfilter%3Ddigest&page=1
http://www.itpub.net/viewthread.php?tid=1077244&extra=&page=1
create
or
replace
function
f_op (p_n1
number
, p_op
varchar2
, p_n2
number
)
return
number
as
begin
return
case
when
p_op =
'+'
then
p_n1 + p_n2
when
p_op =
'-'
then
p_n1 - p_n2
when
p_op =
'*'
then
p_n1 * p_n2
when
p_op =
'/'
and
p_n2<>
0
then
p_n1 / p_n2
else
null
end
;
end
f_op;
/
create
or
replace
procedure
pro_24(p1
number
, p2
number
, p3
number
, p4
number
)
as
r_result
number
default
0
;
begin
for
r
in
(
with
t_num
as
(
select
1
id
,p1
as
n
from
dual
union
select
2
id
,p2
as
n
from
dual
union
select
3
id
,p3
as
n
from
dual
union
select
4
id
,p4
as
n
from
dual),
t_op
as
(
select
'+'
as
o
from
dual
union
select
'-'
as
o
from
dual
union
select
'*'
as
o
from
dual
union
select
'/'
as
o
from
dual)
select
distinct
a.n
as
a,
o1.o
as
o1,
b.n
as
b,
o2.o
as
o2,
c.n
as
c,
o3.o
as
o3,
d.n
as
d
from
t_num a, t_num b, t_num c, t_num d,
t_op o1, t_op o2, t_op o3
where
a.id
not
in
(b.id, c.id, d.id)
and
b.id
not
in
(c.id, d.id)
and
c.id <> d.id)
loop
r_result := f_op(f_op(f_op(r.a,r.o1,r.b),r.o2,r.c),r.o3,r.d);
if
r_result
between
23.9
and
24.1
then
dbms_output.put_line(
'(('
||r.a||r.o1||r.b||
')'
||r.o2||r.c||
')'
||r.o3||r.d);
end
if
;
--((a b) c) d
r_result := f_op(f_op(r.a,r.o1,f_op(r.b,r.o2,r.c)),r.o3,r.d);
if
r_result
between
23.9
and
24.1
then
dbms_output.put_line(
'('
||r.a||r.o1||
'('
||r.b||r.o2||r.c||
'))'
||r.o3||r.d);
end
if
;
--(a (b c)) d
r_result := f_op(f_op(r.a,r.o1,r.b),r.o2,f_op(r.c,r.o3,r.d));
if
r_result
between
23.9
and
24.1
then
dbms_output.put_line(
'('
||r.a||r.o1||r.b||
')'
||r.o2||
'('
||r.c||r.o3||r.d||
')'
);
end
if
;
--(a b) (c d)
r_result := f_op(r.a,r.o1,f_op(f_op(r.b,r.o2,r.c),r.o3,r.d));
if
r_result
between
23.9
and
24.1
then
dbms_output.put_line(r.a||r.o1||
'(('
||r.b||r.o2||r.c||
')'
||r.o3||r.d||
')'
);
end
if
;
--a ((b c) d)
r_result := f_op(r.a,r.o1,f_op(r.b,r.o2,f_op(r.c,r.o3,r.d)));
if
r_result
between
23.9
and
24.1
then
dbms_output.put_line(r.a||r.o1||
'('
||r.b||r.o2||
'('
||r.c||r.o3||r.d||
'))'
);
end
if
;
--a (b (c d))
end
loop
;
end
;
/
exec
pro_24(
3
,
3
,
8
,
8
);
-The End-