@[xsysteven060205](/space/show?uid=140034)
```getsum()``` 里是 ```x+=lowbit(x)```
操作2是```getsum(z)-getsum(y-1)```
by little_gift @ 2018-12-08 21:59:56
@[little_gift](/space/show?uid=22132) 谢谢巨佬
by Naruto_steven @ 2018-12-08 23:53:17