POJ 3107 Godfather 求重心

题目链接

#

题意

思路

#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cstring>
#include<vector>
#include<string>
#include<queue>
#include<stack>
#include<set>
#include<map>
#define ll long long
using namespace std;
const int INF = ( 2e9 ) + 2;
const ll maxn = 5e4+100;
struct edge
{
int v,next;
}e[maxn*2];
int head[maxn];
int tot;
int son[maxn],Max[maxn],ans[maxn];
int Maxsubtree,n;
void add(int u,int v)
{
e[tot].v=v;
e[tot].next=head[u];
head[u]=tot++;
}
void dfs(int u,int fa)
{
son[u]=1;
for(int i=head[u];i!=-1;i=e[i].next)
{
int v=e[i].v;
if(v==fa)continue;
dfs(v,u);
son[u]+=son[v];
Max[u]=max(Max[u],son[v]);
}
Max[u]=max(Max[u],n-son[u]);
if(Maxsubtree>Max[u])
Maxsubtree=Max[u];
}
int main()
{
while(~scanf("%d",&n))
{
memset(head,-1,sizeof(head));
tot=0;
int u,v;
for(int i=1;i<=n-1;i++)
{
scanf("%d%d",&u,&v);
add(u,v);
add(v,u);
}
Maxsubtree=INF;
for(int i=1;i<=n;i++)Max[i]=-INF;
dfs(1,-1);
int cnt=0;
for(int i=1;i<=n;i++)
if(Max[i]==Maxsubtree)
ans[cnt++]=i;
for(int i=0;i<cnt;i++)
if(i!=cnt-1)
printf("%d ",ans[i]);
else
printf("%d\n",ans[i]);
}
}