摘要：
```cpp include include include include include define R(a,b,c) for(register int a = (b); a = (c); a) define Max(a,b) ((a) (b) ? (a) : (b)) define Min( 阅读全文
摘要：
给定一棵有n个点的树，询问树上距离为k的点对是否存在。 a faster way in some cases 阅读全文