@[gghack_m3d](/user/895690) query里
```
return qur(lid,l,r);
```
死循环爆炸
build里
```cpp
if(l == r){
```
没初始化
by Greenzhe @ 2023-01-22 11:59:57
@[Greenzhe](/user/552298) 能详细说说吗？
by gghack_Nythix @ 2023-01-22 12:53:40
@[gghack_m3d](/user/895690)
1：
```cpp
void build_tr(int id,int l,int r){
tr[id].l = l,tr[id].r = r;
if(l == r){
tr[id]=0; //note
return ;
}
int mid = (l + r)>>1;
build_tr(lid,l,mid);
build_tr(rid,mid + 1,r);
tr[id].val = tr[lid].val + tr[rid].val;
}
```
2：
```cpp
int qur(int id,int l,int r){
if(l == tr[id].l && r == tr[id].r){
return tr[id].val;
}
int mid = (tr[id].l + tr[id].r) >> 1;
if(r <= mid){
return qur(lid,l,r);
}
else if(l > mid){
return qur(rid,l,r);
}
else return qur(lid,l,r) + qur(rid,l,r); //note
}
```
说实话这个版本的线段树我有点看不懂（
还有问题建议重学线段树
by Greenzhe @ 2023-01-22 13:40:36
@[Greenzhe](/user/552298) 好吧我过了，我左右移打反了（）（）（）
by gghack_Nythix @ 2023-01-22 13:42:44
@[gghack_m3d](/user/895690) 草草草草草草草草草草草
by Greenzhe @ 2023-01-22 19:46:49