POJ 3107

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<string>
 5 #include<algorithm>
 6 #define MAXN 50010
 7 using namespace std;
 8 typedef struct PP{
 9     int id,par;
10     bool operator < (const PP & a) const{
11         if(par == a.par) return id < a.id;
12         return par < a.par;
13     }
14 }Partition;
15 typedef struct{
16     int to,next;
17 }Node;
18 Node edge[2*MAXN];
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_child(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_child(u);
31     }
32     return cnt[s]--;
33 }
34 void dfs_partition(int s){
35     P[s].id = s;
36     P[s].par = N-cnt[s]-1;
37     vis[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 u,v;
48     while(~scanf("%d",&N)){
49         int k = 1;
50         memset(head,-1,sizeof(head));
51         for(int i = 1;i <= N-1;i ++){
52             scanf("%d%d",&u,&v);
53             addedge(u,v,k++);
54             addedge(v,u,k++);
55         }
56         memset(vis,0,sizeof(vis));
57         dfs_child(1);
58         memset(vis,0,sizeof(vis));
59         dfs_partition(1);
60         sort(P+1,P+N+1);
61         k = 1;
62         while(P[k].par == P[1].par){
63             printf("%d ",P[k].id);
64             k++;
65         }
66         printf("
");
67     }
68     return 0;
69 }