BZOJ 3391 [Usaco2004 Dec]Tree Cutting网络破坏

#include <cstdio>
#include <algorithm>

using std::max;

struct node{
    int u,v,next;
    node(){}
    node(int _u,int _v,int _next){
        u = _u;
        v = _v;
        next = _next;
    }
}Edge[20005];

int n,head[20005],Count;
int sum[20005],Max[20005];

inline void AddEdge(int u,int v){
    Count++;
    Edge[Count] = node(u,v,head[u]);
    head[u] = Count;
}

void dfs(int x,int fa){
    sum[x]=1;
    for(int i=head[x];i;i=Edge[i].next){
        int v = Edge[i].v;
        if(v==fa) continue;
        dfs(v,x);
        sum[x]+=sum[v];
    }    
    for(int i=head[x];i;i=Edge[i].next){
        int v = Edge[i].v;
        Max[x] = max(Max[x],sum[v]);
    }
}

int main(){
    scanf("%d",&n);
    for(int i=1;i<n;i++){
        int u,v;
        scanf("%d%d",&u,&v);
        AddEdge(u,v);
        AddEdge(v,u);
    }
    dfs(1,-1);
    int limit = n/2;
    for(int i=1;i<=n;i++){
        if(n-sum[i]<=limit && Max[i] <= limit ) printf("%d\n",i);
    }
    return 0;
}