??? 很早以前就想用PLSQL寫一個算24點的程序了，后來想了一下沒有研究下去，最近上ITPUB的時候正好大家都在討論，在大牛的基礎上修改了一下，基本上思想和算法都是沒有變的，就是學習了一下。還有兩個大問題沒有處理好，一是只用了枚舉法，用PLSQL應該可以換個更好的遞歸算法的；二是沒有濾重；反正最后的結果只是最簡單的得到答案而已。
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??? 具體的可以參見：
???
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
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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-