树的重心-526互联

const int N=100010;
int n, a, b;
vector<int> e[N];//用vector作邻接表
int siz[N], pos, ans=1e9;
void dfs(int x, int fa){
  siz[x]=1;
  int mx=0;
  for(auto y : e[x]){
    if(y == fa) continue;
    dfs(y, x);//先搜完，再统计答案
    siz[x] += siz[y];
    mx=max(mx, siz[y]);
  }
  mx=max(mx, n-siz[x]);
//维护了重心是pos
  if(mx<ans) ans=mx,pos=x;
}
int main(){
  scanf("%d", &n);
  for(int i=1;i<n;i++){
    scanf("%d%d",&a,&b);
    e[a].push_back(b);
    e[b].push_back(a);
  }
  dfs(1, 0);
  printf("%d\n",ans);
  return 0;
}