hdu 4607 Park Visit (dfs)

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=4607

首先如果k小于等于直径长度，那么答案为k−1。如果k大于直径长度，设直径长度为r，那么答案为r−1+(k−r)∗2。

 #include <cstdio>
 #include <cmath>
 #include <algorithm>
 #include <iostream>
 #include <cstring>
 #include <queue>
 #include <vector>
 #define maxn 105000
 using namespace std;

 const int INF = 0x3f3f3f;

 vector<int> G[maxn];
 int N,M;
 int maxdeep,point;
 bool vis[maxn];
 void dfs(int u,int deep){
     if(maxdeep < deep){
         maxdeep = deep;
         point = u;
     }
     for(int i=;i<G[u].size();i++){
        int v = G[u][i];
        if(!vis[v]){
          vis[v] = true;   //printf("u,v  %d %d\n",u,v);jf
          dfs(v,deep+);
        }
     }
 }

 int main()
 {
     //if(freopen("input.txt","r",stdin)== NULL)  {printf("Error\n"); exit(0);}

     int T;
     cin>>T;
     while(T--){
         cin>>N>>M;
         if(N == ){
             for(int i=;i<=M;i++){
                 int K;
              scanf("%d",&K);
              printf("0\n");
                }
             continue;
         } 

         for(int i=;i<=N;i++)   G[i].clear();
         for(int i=;i<=N-;i++){
             int a,b;
             scanf("%d %d",&a,&b);
             G[a].push_back(b);
             G[b].push_back(a);
         }
         memset(vis,,sizeof(vis));
         maxdeep = ; point = ;
         vis[] = true;
         dfs(,);
         memset(vis,,sizeof(vis));
         dfs(point,);
         for(int i=;i<=M;i++){
             int K;
             scanf("%d",&K);
             if(maxdeep >= K-) printf("%d\n",K-);
             else           printf("%d\n",maxdeep +  * (K -  - maxdeep));
         }
     }
 }