还有,不要把
```cpp
if(l>r) return ;
```
写成
```cpp
if(r>l) return ;
```
/fn/fn/fn
by BFSDFS123 @ 2023-01-14 22:01:33
还有,c++中尽量在printf中写("%2d ")(加个空格)
by J_Jack @ 2023-01-14 22:24:03