algorithm - 有没有一种算法可以将一个数字分成三部分，并使它们的总和与原始数字相匹配？

Question

例如，如果您考虑以下示例。

100.00 - Original Number
33.33  - 1st divided by 3
33.33  - 2nd divided by 3
33.33  - 3rd divided by 3
99.99  - Is the sum of the 3 division outcomes

But i want it to match the original 100.00

我看到的一种方法是将原始数字减去前两个部分，结果将是我的第三个数字。现在，如果我取这 3 个数字，我就会得到我原来的数字。

 100.00 - Original Number
  33.33 - 1st divided by 3
  33.33 - 2nd divided by 3
  33.34 - 3rd number
 100.00 - Which gives me my original number correctly. (33.33+33.33+33.34 = 100.00)

在 Oracle PL/SQL 中是否有一个公式或一个函数或可以实现的东西？

提前致谢!

Answer 1

此版本也将精度作为参数:

with q as (select 100 as val, 3 as parts, 2 as prec from dual)
select rownum as no
      ,case when rownum = parts
       then val - round(val / parts, prec) * (parts - 1) 
       else round(val / parts, prec)
       end v
from   q
connect by level <= parts

no  v
=== =====
1   33.33
2   33.33
3   33.34

例如，如果您想将值拆分为当月的天数，您可以这样做:

with q as (select 100 as val
                 ,extract(day from last_day(sysdate)) as parts
                 ,2 as prec from dual)
select rownum as no
      ,case when rownum = parts
       then val - round(val / parts, prec) * (parts - 1) 
       else round(val / parts, prec)
       end v
from   q
connect by level <= parts;

1   3.33
2   3.33
3   3.33
4   3.33
...
27  3.33
28  3.33
29  3.33
30  3.43

要按每个月的天数加权在每个月之间分配值，您可以改为这样做(更改 level <= 3 以更改计算的月数):

with q as (
  select add_months(date '2013-07-01', rownum-1) the_month
        ,extract(day from last_day(add_months(date '2013-07-01', rownum-1)))
         as days_in_month
        ,100 as val
        ,2 as prec
  from dual
  connect by level <= 3)
,q2 as (
  select the_month, val, prec
        ,round(val * days_in_month 
                     / sum(days_in_month) over (), prec)
         as apportioned
        ,row_number() over (order by the_month desc) 
         as reverse_rn
  from   q)
select the_month
      ,case when reverse_rn = 1
       then val - sum(apportioned) over (order by the_month
                  rows between unbounded preceding and 1 preceding)
       else apportioned
       end as portion
from q2;

01/JUL/13   33.7
01/AUG/13   33.7
01/SEP/13   32.6