bzoj3391 [Usaco2004 Dec]Tree Cutting网络破坏（dfs）

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define inf 0x3f3f3f3f
#define N 10010
inline int read(){
int x=0,f=1;char ch=getchar();
while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
while(ch>='0'&&ch<='9') x=x*10+ch-'0',ch=getchar();
return x*f;
}
int n,h
,num=0,size
,fa
;
bool f
;
struct edge{int to,next;}data[N<<1];
void dfs(int x){
size[x]=1;
for(int i=h[x];i;i=data[i].next){
int y=data[i].to;
if(y==fa[x]) continue;
fa[y]=x;dfs(y);size[x]+=size[y];
if(size[y]>n/2) f[x]=0;
}
if(n-size[x]>n/2) f[x]=0;
}
int main(){
//  freopen("a.in","r",stdin);
n=read();memset(f,1,sizeof(f));
for(int i=1;i<n;++i){
int x=read(),y=read();
data[++num].to=y;data[num].next=h[x];h[x]=num;
data[++num].to=x;data[num].next=h[y];h[y]=num;
}
dfs(1);
for(int i=1;i<=n;++i)
if(f[i]) printf("%d\n",i);
return 0;
}