关于那道趣的算法题：实现24点游戏求解的存储过程
我也写了一个，跟大家分享一下:)
--保存运算符之间的优先级，通过该表可以判断在一个表达式中加上一对括号是否会改变表达式的值。
create table t_operator (operator1 char(1),operator2 char(1),flag int)
insert t_operator(operator1,operator2,flag)
select '- ', '+ ', '2 ' union all select '- ', '- ', '2 ' union all select '/ ', '* ', '2 ' union all
select '/ ', '/ ', '2 ' union all select '* ', '+ ', '2 ' union all select '* ', '- ', '2 ' union all
select '/ ', '+ ', '2 ' union all select '/ ', '- ', '2 ' union all select '+ ', '* ', '1 ' union all
select '+ ', '/ ', '1 ' union all select '- ', '* ', '1 ' union all select '- ', '/ ', '1 '
go
create proc p_calc_24 @a int,@b int,@c int,@d int
as
/*
描述：
给定任意四个整数，保持数字顺序不变,在数字中间加入+-* /()等符号,使表达式等于24，括号最多加4-2=2对。
版本：
时间 修改人 操作
2007年05月21日 mengmou 创建
输入参数：
任意四个整数.
涉及:
表t_operator，保存运算符之间的优先级，通过该表可以判断在一个表达式中加上一对括号是否会改变表达式的值。
返回：
所有满足条件的表达式的结果集。
BUG：
1.表达式[8+13-9*2]⑴派生出[(8+13-9)*2]⑵和[8+(13-9)*2]⑶，表达式⑶又派生出[(8+(13-9))*2]⑷，
表达式⑷中的内层括号并不影响⑷的值，⑷相当于⑵的冗余，所以像⑷这类冗余不应该出现在结果集中。
四个整数的表达式最多有两对括号，如果一一列举出所有情况并判断是否为冗余，会使代码会非常臃肿。
*/
set nocount on
set arithabort off
set arithignore off
set ansi_warnings off
declare @operator_list varchar(4),@x int,@y int,@z int,@i int,@sql nvarchar(50),@result numeric(38,6)
,@aa varchar(10),@bb varchar(10),@cc varchar(10),@dd varchar(10),@xx char(1),@yy char(1),@zz char(1)
,@id int,@operator varchar(8000),@group_id int,@new_operator varchar(8000),@min_id int,@max_id int
,@old_group_id int,@new_group_id int
select @aa = convert(varchar(10),@a)+ '.0 ',@bb = convert(varchar(10),@b)+ '.0 ',@cc = convert(varchar(10),@c)+ '.0 '
,@dd = convert(varchar(10),@d)+ '.0 ',@operator_list = '-+/* ',@x = 1,@y = 1,@z = 1,@i = 1,@new_operator = ' '
,@new_group_id = 1,@old_group_id = 0
declare @t_expression table(expression varchar(50))
declare @t_operator table(group_id int,id int identity,operator varchar(8000))
while @x <= 4
begin
while @y <= 4
begin
while @z <= 4--增加嵌套循环的层数便可以实现在N个数中间加上+-*/()使表达式等于M，括号最多加N-2对。
begin
select @xx = substring(@operator_list,@x,1),@yy = substring(@operator_list,@y,1)
,@zz = substring(@operator_list,@z,1)
,@sql = 'select @result = '+ @aa + @xx + @bb + @yy + @cc + @zz + @dd
exec sp_executesql @sql,N '@result numeric(38,6) out ',@result out
if @result = 24.00000
begin
insert @t_expression(expression) select replace(stuff(@sql,1,16, ' '), '.0 ', ' ')
end
else--去掉else中的代码返回只有加减乘除没有括号的表达式
begin
insert @t_operator
select @new_group_id,@aa union all select @new_group_id,@xx union all select @new_group_id,@bb union all
select @new_group_id,@yy union all select @new_group_id,@cc union all select @new_group_id,@zz union all
select @new_group_id,@dd
set @new_group_id = @new_group_id + 1
loop1:
declare c_suited_id cursor for
select distinct _a.group_id
,case when exists(select 1 from t_operator where flag = 1 and operator1 = _a.operator and operator2 = _b.operator)
then _a.id-1 else _a.id+1 end as min_id
,case when exists(select 1 from t_operator where flag = 1 and operator1 = _a.operator and operator2 = _b.operator)
then _b.id-1 else _b.id+1 end as max_id
from @t_operator _a
join @t_operator _b on _b.id > _a.id and _b.group_id = _a.group_id
where _a.group_id > = @old_group_id and _b.group_id > = @old_group_id
and _a.operator in ( '+ ', '- ', '* ', '/ ') and _b.operator in ( '+ ', '- ', '* ', '/ ')
and exists(select 1 from t_operator where operator1 = _a.operator and operator2 = _b.operator )
set @old_group_id = @new_group_id
open c_suited_id
fetch next from c_suited_id into @group_id,@min_id,@max_id
while @@fetch_status = 0
begin
set @new_operator = ' '
select @new_operator = @new_operator + operator
from @t_operator
where group_id = @group_id and id between @min_id and @max_id
insert @t_operator(group_id,operator)
select @new_group_id,*
from (
select operator from @t_operator where group_id = @group_id and id < @min_id union all
select '( '+@new_operator+ ') ' union all
select operator from @t_operator where group_id = @group_id and id > @max_id
) x
select @sql = ' '
select @sql = @sql + operator from @t_operator where group_id = @new_group_id order by id
select @sql = 'select @result = ' + @sql
exec sp_executesql @sql,N '@result numeric(38,6) out ',@result out
if @result = 24.00000
insert @t_expression(expression) select replace(stuff(@sql,1,16, ' '), '.0 ', ' ')
set @new_group_id = @new_group_id + 1
fetch next from c_suited_id into @group_id,@min_id,@max_id
end
close c_suited_id
deallocate c_suited_id
if @old_group_id < @new_group_id
goto loop1
delete @t_operator
end
set @z = @z + 1
end
select @y = @y + 1,@z = 1
end
select @x = @x + 1,@y = 1,@z = 1
end
select distinct * from @t_expression order by expression
go
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有问题吗？
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呀~在网吧~~没环境~~~~~~只是对你说的方式不认同！！偶也很不喜欢滥用IF
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偶路过...
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