POJ -- 1655

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<string>
 5 #include<algorithm>
 6 #define MAXN 20010
 7 using namespace std;
 8 typedef struct{
 9     int to,next;
10 }Node;
11 typedef struct PP{
12     int id,par;
13     bool operator < (const PP &a) const {
14         if(par == a.par) return id < a.id;
15         return par < a.par;
16     }
17 }Partition;
18 Node edge[MAXN*2];
19 Partition P[MAXN];
20 int head[MAXN],vis[MAXN],cnt[MAXN],N;
21 void addedge(int u,int v,int k){
22     edge[k].to = v;
23     edge[k].next = head[u];
24     head[u] = k;
25 }
26 int dfs(int s){
27     vis[s] = cnt[s] = 1;
28     for(int i = head[s];~i;i = edge[i].next){
29         int u = edge[i].to;
30         if(!vis[u]) cnt[s] += dfs(u);
31     }
32     return cnt[s]--;
33 }
34 void dfs_partition(int s){
35     vis[s] = 1;
36     P[s].id  =s;
37     P[s].par = N - cnt[s] - 1;
38     for(int i = head[s];~i;i = edge[i].next){
39         int u = edge[i].to;
40         if(!vis[u]){
41             P[s].par = max(P[s].par,cnt[u]+1);
42             dfs_partition(u);
43         }
44     }
45 }
46 int main(){
47     int t,u,v;
48 //    freopen("in.c","r",stdin);
49     scanf("%d",&t);
50     while(t--){
51         memset(head,-1,sizeof(head));
52         scanf("%d",&N);
53         int k = 1;
54         for(int i = 1;i <= N-1;i ++){
55             scanf("%d%d",&u,&v);
56             addedge(u,v,k++);
57             addedge(v,u,k++);
58         }
59         memset(vis,0,sizeof(vis));
60         dfs(1);
61         memset(vis,0,sizeof(vis));
62         dfs_partition(1);
63         sort(P+1,P+N+1);
64         printf("%d %d
",P[1].id,P[1].par);
65     }
66     return 0;
67 }