听不懂您的问题
```cpp
// luogu-judger-enable-o2
#include <cstdio>
#include <cstring>
#include <cmath>
#include <iostream>
#include <algorithm>
using namespace std;
inline long long read(){
long long f=1,x=0;
char c=getchar();
while (c<'0'||c>'9'){if(c=='-') f=-1;c=getchar();}
while (c>='0'&&c<='9'){x=x*10+c-'0';c=getchar();}
return f*x;
}
const long long maxn=1e6+5;
long long n,m,g,h,o,p,cnt,sum;
long long dep[maxn],siz[maxn],nxt[maxn*2],s[maxn*2],lnk[maxn],f[maxn];
long long ans[maxn];
inline void add(long long x,long long y){
cnt++;
s[cnt]=y;
nxt[cnt]=lnk[x];
lnk[x]=cnt;
}
void dfs(long long x,long long y){
siz[x]=1,f[x]=y;dep[x]=dep[y]+1;
sum+=dep[x];
for (long long i=lnk[x];i>-1;i=nxt[i]){
if (s[i]==y) continue;
dfs(s[i],x);
siz[x]+=siz[s[i]];
}
}
void search(long long x,long long y){
for (long long i=lnk[x];i>-1;i=nxt[i]){
if (s[i]==y) continue;
ans[s[i]]=ans[x]+n-2*siz[s[i]];
search(s[i],x);
}
}
int main(){
memset(lnk,-1,sizeof(lnk));
n=read();
for (long long i=1;i<n;i++){
long long x=read(),y=read();
add(x,y);
add(y,x);
}
dfs(1,0);
ans[1]=sum-n;
// printf("%lld\n",ans[1]);
search(1,0);
long long mx=-1e16;
for (long long i=1;i<=n;i++)
if (ans[i]>mx) mx=ans[i],p=i;
printf("%lld",p);
return 0;
}
```
by wizard（偷开O2 @ 2020-11-02 20:55:23
就是好奇为什么题解里面说树的直径是可以AC的
以及如果真的可行那我的错误在哪里
谢谢
by Ricardo_21 @ 2020-11-02 21:05:29