```cpp
void pushdown(ll x,ll l,ll r){
ll mid=(l+r)/2;
a[x*2].delta+=a[x].delta;
a[x*2+1].delta+=a[x].delta;
a[x*2].sum+=a[x].delta*(mid-l+1);
a[x*2+1].sum+=a[x].delta*(r-mid); // mid + 1 ~ r 共有 (r - mid) 个数
a[x].delta=0;
}
```
by DGH_Didi @ 2023-12-12 19:51:25
谢谢大佬，明白了，当时纯属脑残
by lutaoquan2012 @ 2023-12-12 19:54:34