POJ 3107

 #include<iostream>
 #include<cstdio>
 #include<cstring>
 #include<string>
 #include<algorithm>
 #define MAXN 50010
 using namespace std;
 typedef struct PP{
     int id,par;
     bool operator < (const PP & a) const{
         if(par == a.par) return id < a.id;
         return par < a.par;
     }
 }Partition;
 typedef struct{
     int to,next;
 }Node;
 Node edge[*MAXN];
 Partition P[MAXN];
 int head[MAXN],vis[MAXN],cnt[MAXN],N;
 void addedge(int u,int v,int k){
     edge[k].to = v;
     edge[k].next = head[u];
     head[u] = k;
 }
 int dfs_child(int s){
     vis[s] = cnt[s] = ;
     for(int i = head[s];~i;i = edge[i].next){
         int u = edge[i].to;
         if(!vis[u]) cnt[s] += dfs_child(u);
     }
     return cnt[s]--;
 }
 void dfs_partition(int s){
     P[s].id = s;
     P[s].par = N-cnt[s]-;
     vis[s] = ;
     for(int i = head[s];~i;i = edge[i].next){
         int u = edge[i].to;
         if(!vis[u]){
             P[s].par = max(P[s].par,cnt[u]+);
             dfs_partition(u);
         }
     }
 }
 int main(){
     int u,v;
     while(~scanf("%d",&N)){
         int k = ;
         memset(head,-,sizeof(head));
         for(int i = ;i <= N-;i ++){
             scanf("%d%d",&u,&v);
             addedge(u,v,k++);
             addedge(v,u,k++);
         }
         memset(vis,,sizeof(vis));
         dfs_child();
         memset(vis,,sizeof(vis));
         dfs_partition();
         sort(P+,P+N+);
         k = ;
         while(P[k].par == P[].par){
             printf("%d ",P[k].id);
             k++;
         }
         printf("\n");
     }
     return ;
 }