Puzzleup 2013挑战赛即将开始

udfrog

哦，是125

newkid

你到底看明白没有？我这方法有问题吗？

udfrog

newkid 发表于 2013-11-14 09:20
你到底看明白没有？我这方法有问题吗？

恩，你这个125的N按这个方法是可以做到的。感觉也没有比这还大的了。
思路不像40岁的老年人啊~~~

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No: 18       November 20, 2013  



Three Prime Numbers

Three Prime Numbers

There are three 2-digit prime numbers.
-The arithmetic mean of these three numbers are prime.
-The arithmetic mean of each pair is prime.
Find these three numbers.

Enter the three numbers from the smallest to the largest, with commas between them.

〇〇

〇〇 发表于 2013-11-20 19:22
No: 18       November 20, 2013  

写了个较差的，求优化
with t as(select 2*level+1 a from dual connect by level<50),
p as (select a from t
minus
select t1.a*t2.a from t t1,t t2 where t1.a<10 and t2.a<10)
select p.a,p1.a,p2.a from p,p p1,p p2
where p.a<p1.a and p1.a<p2.a
and (p.a+p1.a)/2 in (select a from p)
and (p1.a+p2.a)/2 in (select a from p)
and (p.a+p2.a)/2 in (select a from p)
and (p.a+p1.a+p2.a)/3 in (select a from p)
;

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p中忘记删除1位的,minus的东西也少了
  
   71    79    99
   69    89    97
   73    85    97
   75    91    95
   83    87    91
   79    87    95
   77    93    97
   85    89    93
   79    95    99
   87    91    95
   83    91    99
   89    93    97
   91    95    99

已选择290行。

已用时间:  00: 20: 23.19

〇〇

SQL> with t as(select 2*level+1 a from dual connect by level<50),
  2   p as (select a from t where a>10
  3   minus
  4   select t1.a*t2.a from t t1,t t2 )
  5  select p.a,p1.a,p2.a from p,p p1,p p2
  6  where p.a<p1.a and p1.a<p2.a
  7  and (p.a+p1.a)/2 in (select a from p)
  8  and (p1.a+p2.a)/2 in (select a from p)
  9  and (p.a+p2.a)/2 in (select a from p)
10  and (p.a+p1.a+p2.a)/3 in (select a from p)
11  ;

    A     A     A
----- ----- -----
   11    47    71

〇〇

〇〇 发表于 2013-11-20 19:59
SQL> with t as(select 2*level+1 a from dual connect by level10
  3   minus
  4   select t1.a*t2.a  ...

前面这个50秒
下面这个0.04秒
with t as(select 2*level+1 a from dual connect by level<50),
p as (select a from t where a>10
minus
select t1.a*t2.a from t t1,t t2 ),
p2 as (select p.a,p1.a b from p,p p1 where  p.a<p1.a and (p.a+p1.a)/2 in (select a from p))
select a.a,a.b,b.b from p2 a,p2 b where a.b=b.a and (a.a+a.b+b.b)/3 in (select a from p)
and (a.a,b.b) in (select a,b from p2);

〇〇

〇〇 发表于 2013-11-20 19:59
SQL> with t as(select 2*level+1 a from dual connect by level10
  3   minus
  4   select t1.a*t2.a  ...

前面这个50秒
下面这个0.04秒
with t as(select 2*level+1 a from dual connect by level<50),
p as (select a from t where a>10
minus
select t1.a*t2.a from t t1,t t2 ),
p2 as (select p.a,p1.a b from p,p p1 where  p.a<p1.a and (p.a+p1.a)/2 in (select a from p))
select a.a,a.b,b.b from p2 a,p2 b where a.b=b.a and (a.a+a.b+b.b)/3 in (select a from p)
and (a.a,b.b) in (select a,b from p2);

newkid

最近的题都很容易。
那个50的写法有点怪，明明才21个素数。如果把p改成实体表就很快。这应该是优化器的问题。