POJ 2378 Tree Cutting

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <vector>
 5 #include <algorithm>
 6 using namespace std;
 7 const int maxn = 10010;
 8 vector<int>g[maxn],ans;
 9 int n,m,son[maxn];
10 void dfs(int u,int fa){
11     son[u] = 1;
12     int maxson = 0;
13     for(int i = g[u].size()-1; i >= 0; --i){
14         if(g[u][i] == fa) continue;
15         dfs(g[u][i],u);
16         maxson = max(maxson,son[g[u][i]]);
17         son[u] += son[g[u][i]];
18     }
19     maxson = max(maxson,n - son[u]);
20     if(maxson <= (n>>1)) ans.push_back(u);
21 }
22 int main(){
23     int u,v;
24     while(~scanf("%d",&n)){
25         for(int i = 0; i <= n; ++i) g[i].clear();
26         for(int i = 1; i < n; ++i){
27             scanf("%d%d",&u,&v);
28             g[u].push_back(v);
29             g[v].push_back(u);
30         }
31         ans.clear();
32         dfs(1,-1);
33         if(ans.size()){
34             sort(ans.begin(),ans.end());
35             for(int i = 0; i < ans.size(); ++i)
36                 printf("%d\n",ans[i]);
37         }else puts("NONE");
38     }
39     return 0;
40 }