POJ 1691 dfs

http://poj.org/problem?id=1655

跟3107差不多

代码：

#include<iostream>
#include<cstdio>
#include<string>
#include<cstring>
#define Min(a,b)a<b?a:b
#define Max(a,b)a>b?a:b
#define MAX 20005
using namespace std;
int head[MAX],sumVal[MAX];
int n,s_edge,ans_node,ans_cnt;
bool vs[MAX];
struct Edge
{
    int to,nxt;
}edge[MAX*2];

void addedge(int u,int v)
{
    s_edge++;
    edge[s_edge].to=v;
    edge[s_edge].nxt=head[u];
    head[u]=s_edge;

    s_edge++;
    edge[s_edge].to=u;
    edge[s_edge].nxt=head[v];
    head[v]=s_edge;
}

void dfs(int x)
{
   vs[x]=1;
   sumVal[x]=1;
   int maxSub=0,SUM;
   for(int e=head[x];e;e=edge[e].nxt)
   {
       int v=edge[e].to;
       if(!vs[v])
       {
           dfs(v);
           sumVal[x]+=sumVal[v];
           maxSub=Max(maxSub,sumVal[v]);
       }
   }
   SUM=Max(maxSub,n-sumVal[x]);
   if(SUM<ans_cnt)
   {
       ans_cnt=SUM;
       ans_node=x;
   }
}

int main()
{
    int CASE,i,a,b;
    scanf("%d",&CASE);
    while(CASE--)
    {
        scanf("%d",&n);
        s_edge=0;
        memset(head,0,sizeof(head));
        memset(vs,0,sizeof(vs));
        for(i=1;i<n;i++)
        {
          scanf("%d%d",&a,&b);
          addedge(a,b);
        }

        ans_cnt=MAX;
        dfs(1);
        printf("%d %d\n",ans_node,ans_cnt);
    }
    return 0;
}