codeforces 120F Spiders 树形DP

#include <cstdio>
#include <cstring>
#include <utility>
#include <vector>
#include <algorithm>
#include <iostream>
#define LMT 102
using namespace std;
bool gra[LMT][LMT];
int dis[LMT];
vector< pair<int,int> >gr[LMT];
int n;
bool cmp( pair<int,int> a,pair<int,int>b)
{
    if(a.second!=b.second)return a.second<b.second;
    return a.first<b.first;
}
void inidfs(int u,int pre)
{
    for(int v=0;v<n;v++)
    if(v!=pre&&gra[u][v])
    {
        inidfs(v,u);
       if(gr[v].size()>0)
       {
           pair<int,int> p=gr[v][gr[v].size()-1];
           gr[u].push_back(make_pair(v,p.second+1));
       }
       else gr[u].push_back(make_pair(v,1));
    }
   if(gr[u].size()>0)
    sort(gr[u].begin(),gr[u].end(),cmp);
}
void dfs(int u,int pre)
{
    int siz;
   if(pre!=-1)
   {
       dis[u]=dis[pre]+1;
       siz=gr[pre].size();
        if(siz>0&&u==gr[pre][siz-1].first)
      {
         if(siz>1&&dis[u]<gr[pre][siz-2].second+1)
         dis[u]=gr[pre][siz-2].second+1;
      }
      else if(siz>0&&dis[u]<gr[pre][siz-1].second+1)dis[u]=gr[pre][siz-1].second+1;
   }
    for(int v=0;v<n;v++)
      if(v!=pre&&gra[u][v])
       dfs(v,u);
}
int solve(void)
{
   int ret=-1;
   for(int i=0;i<n;i++)gr[i].clear();
   memset(dis,0,sizeof(dis));
   inidfs(0,-1);
   ret=gr[0][gr[0].size()-1].second;
   dfs(0,-1);
   for(int i=0;i<n;i++)
     ret=ret>dis[i]?ret:dis[i];
   return ret;
}
int main()
{
    freopen("input.txt","r",stdin);
   freopen("output.txt","w",stdout);
    int N,ans=0;
    scanf("%d",&N);
    while(N--)
    {
        memset(gra,0,sizeof(gra));
        scanf("%d",&n);
        for(int i=0;i<n-1;i++)
        {
            int u,v;
            scanf("%d%d",&u,&v);
            u--;v--;
            gra[u][v]=gra[v][u]=1;
        }
        ans+=solve();
    }
    printf("%d\n",ans);
    return 0;
}