@[guodong](/space/show?uid=81372) 来自USACO官网的样例解释:
```
Two possible pedigrees have 5 nodes and height equal to 3:
@ @
/ \ / \
@ @ and @ @
/ \ / \
@ @ @ @
```
by 01190220csl @ 2019-10-19 19:01:40
你不是都说了只有两种形态/jk，所以是2啊
by Provicy @ 2019-11-25 17:56:03