AC on #1 # 7

其余WA

#include<iostream>
#include<cstring>
#include<algorithm>
#include<vector>
using namespace std;
const int N = 100010;
vector<int> g[N];
int n;
int d[2][N];
int from[2][N];
int up[N];
int res = 1e9 , x , ans;
void dfs1(int u , int father){
	d[0][u] = d[1][u] = 0;
	for(auto node : g[u]){
		int j = node , w = 1;
		if(j == father) continue;
		dfs1(j , u);
		if(d[0][j] + w >= d[0][u]){
			d[1][u] = d[0][u];
			d[0][u] = d[0][j] + w;
			from[1][u] = from[0][u];
			from[0][u] = j;
		}
		else if(d[0][j] + w > d[1][u]){
			d[1][u] = d[0][j] + w;
			from[1][u] = j;
		}
	}
}
void dfs2(int u , int father){
	for(auto node : g[u]){
		int j = node , w = 1;
		if(j == father) continue;
		if(from[0][u] == j) up[j] = max(up[u] , d[1][u]) + w;
		else up[j] = max(up[u] , d[0][u]) + w;
		dfs2(j , u);
	}
}
int vis[N];
int dist[N];
void dfs3(int u){
	for(auto node : g[u]){
		int j = node , w = 1;
		if(!vis[j]){
			dist[j] = dist[u] + w;
			vis[j] = 1;
			dfs3(j);
		}
	}
}
int main(){
	cin >> n;
	for(int i = 1;i < n;i++){
		int u , v;
		scanf("%d%d" , &u , &v);
		g[u].push_back(v);
		g[v].push_back(u);
	}
	dfs1(1 , -1);
	dfs2(1 , -1);
	for(int i = 1;i <= n;i++){
		if(max(d[0][i] , up[i]) < res){
			res = max(d[0][i] , up[i]);
			x = i;
		}
	}
	vis[x] = 1;
	dist[x] = 0;
	dfs3(x);
	for(int i = 1;i <= n;i++) ans += dist[i];
	cout << x << " " << ans << endl;
	return 0;
}