@[zfy2006](/user/574890)
```cpp
for(;x<=cnt;x+=x&-x)c[x]+=k;
```
应该改成
```cpp
for(;x<=num;x+=x&-x)c[x]+=k;
```
你的 dfn 序会算上根节点，所以值域比 $cnt$ 多 $1$。
by sleeping_crawlers @ 2022-06-02 16:03:17
@[sleeping_crawlers](/user/148404) $\text{\Huge{听我说谢谢您，因为有您!}}$
by zfy2006 @ 2022-06-02 16:13:46
@[zfy2006](/user/574890) ！
by Altwilio @ 2022-06-02 21:03:18
@[zfy2006](/user/574890) /bx
by Tibrella @ 2023-06-08 21:23:23