```cpp
if(pos[a.r]!=pos[a.r]){
```
应该是
```cpp
if(pos[a.r]!=pos[b.r]){
```
![](https://cdn.luogu.com.cn/upload/image_hosting/smkuw2bm.png)![](https://cdn.luogu.com.cn/upload/image_hosting/smkuw2bm.png)![](https://cdn.luogu.com.cn/upload/image_hosting/smkuw2bm.png)我是消愁
by TempestMiku @ 2023-05-30 10:26:41