PUZZLEUP 2015

lugionline · 发表于 2015-9-24 08:27

这题sql最合适了，手算也不是什么问题

solomon_007 · 发表于 2015-9-24 11:18

9#

以OO的 211#的结点命名为基础:

SQL> with t1 as (
  2          select 'A' START_NODE,'C' END_NODE from dual
  3          union all
  4          select 'A','E' from dual
  5          union all
  6          select 'A','M' from dual
  7          union all
  8          select 'C','D' from dual
  9          union all
10          select 'C','F' from dual
11          union all
12          select 'E','F' from dual
13          union all
14          select 'E','G' from dual
15          union all
16          select 'G','O' from dual
17          union all
18          select 'G','M' from dual
19          union all
20          select 'D','M' from dual
21          union all
22          select 'D','O' from dual
23          union all
24          select 'F','O' from dual),
25    t2 as (
26          select 'O' START_NODE,'L' END_NODE from dual
27          union all
28          select 'O','H' from dual
29          union all
30          select 'O','N' from dual
31          union all
32          select 'L','K' from dual
33          union all
34          select 'L','J' from dual
35          union all
36          select 'H','J' from dual
37          union all
38          select 'H','I' from dual
39          union all
40          select 'I','B' from dual
41          union all
42          select 'I','N' from dual
43          union all
44          select 'K','N' from dual
45          union all
46          select 'K','B' from dual
47          union all
48          select 'J','B' from dual),
49    t as (
50          select start_node,end_node
51             from t1
52          union all
53          select end_node start_node, start_node end_node
54             from t1
55          union all
56          select start_node,end_node
57             from t2
58          union all
59          select end_node start_node, start_node end_node
60             from t2),
61    s as (
62  select level lvl,replace(sys_connect_by_path(start_node,','),',','') node_path
63 from t
64 where level >= 6
65  connect by nocycle prior start_node = end_node
66 start with start_node = 'A')
67  select count(distinct node_path)
68 from s
69 where substr(node_path,length(node_path),1) = 'B'
70  /
COUNT(DISTINCTNODE_PATH)
------------------------
                  324