@[BLUE_EYE](/space/show?uid=58354) 注意看
```cpp
void dfs1(int x){
size[x] = 1;de[x] = de[fa[x]] + 1;
for(int i=head[x];i;i=a[i].next){
int to = a[i].to;
if(to == fa[x]) continue;
fa[to] = x;
dfs1(to);
size[to] += size[x];
if(size[to] > size[son[x]]) son[x] = to;
}
}
```
把
```cpp
size[to] += size[x];
```
改成
```cpp
size[x] += size[to];
```
因为size[x]记录的是以x为根的树的结点数量，选重儿子肯定要选子树的size[v]最大的子结点呀。
by throusea @ 2018-11-09 09:05:18
@[throusea](/space/show?uid=59951) 然后他TLE了。。。。。我也发现了这个，但是加上去开O2MLE,不开TLE
by Thosaka_Forest @ 2018-11-09 09:06:01
@[g21glf](/space/show?uid=31639) 竟然还有！
by throusea @ 2018-11-09 09:06:48
@[BLUE_EYE](/space/show?uid=58354) ok你犯了两个错，一个是上面那位巨佬指出的
by Thosaka_Forest @ 2018-11-09 09:08:16
另一个是这一段：
```cpp
void dfs2(int x){
id[x] = ++cnt;id_map[cnt] = x;
if(x == son[fa[x]]) top[x] = top[fa[x]];
else top[x] = x;
if(son[x]) dfs2(son[x]);
for(int i=head[x];i;i=a[i].next){
int to = a[i].to;
if(son[to] == to || to == fa[x]) continue;
dfs2(to);
}
}
```
应该是if(son[x]==to.....)，因为x的重儿子已经dfs过了，所以遇到他的重儿子就跳过
by Thosaka_Forest @ 2018-11-09 09:09:33
@[throusea](/space/show?uid=59951) 找出来了qwq
by Thosaka_Forest @ 2018-11-09 09:09:43
@[throusea](/space/show?uid=59951) 还有一个
```cpp
if(son[to] == to || to == fa[x]) continue;
```
这里很明显是son[x]好吧。不知道你有没有理解树剖。
交上去A了。
by throusea @ 2018-11-09 09:10:23
QAQ 蒟蒻太久没打树剖练板子没想到这么多错
by BLUE_EYE @ 2018-11-09 09:14:00
变成轻链剖分了
by BLUE_EYE @ 2018-11-09 09:14:27
谢谢大佬们 @[throusea](/space/show?uid=59951) @[g21glf](/space/show?uid=31639)
by BLUE_EYE @ 2018-11-09 09:19:10