B07 DFS 树的重心

视频链接：E32 树形DP 树的重心_哔哩哔哩_bilibili

 

#include <iostream>
#include <cstring>
#include <algorithm>
#include <vector>
using namespace std;

const int N=100010;
int n, a, b;
vector<int> e[N];
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);
    siz[x] += siz[y];
    mx=max(mx, siz[y]);
  }
  mx=max(mx, n-siz[x]);
  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 %d\n",pos,ans);
  return 0;
}