题解报告：hdu 4607 Park Visit（最长路+规律）

 1 #include<iostream>
 2 #include<string.h>
 3 #include<cstdio>
 4 using namespace std;
 5 const int maxn=1e5+5;
 6 struct EDGE{int to,next;}edge[maxn<<1];
 7 int t,n,m,k,x,y,cnt,res,maxdist,head[maxn];
 8 void add_edge(int u,int v){
 9     edge[cnt].to=v;
10     edge[cnt].next=head[u];
11     head[u]=cnt++;
12 }
13 int dfs(int u,int fa,int &maxdist){
14     int Dmax=0,Dsec=0;
15     for(int i=head[u];~i;i=edge[i].next){
16         int v=edge[i].to;
17         if(v^fa){
18             int nowd=dfs(v,u,maxdist)+1;
19             if(nowd>Dmax)Dsec=Dmax,Dmax=nowd;
20             else if(nowd>Dsec)Dsec=nowd;
21         }
22     }
23     maxdist=max(maxdist,Dmax+Dsec);
24     return Dmax;
25 }
26 int main(){
27     while(~scanf("%d",&t)){
28         while(t--){
29             scanf("%d%d",&n,&m);
30             memset(head,-1,sizeof(head));cnt=maxdist=0;
31             while(--n){
32                 scanf("%d%d",&x,&y);
33                 add_edge(x,y);
34                 add_edge(y,x);
35             }
36             dfs(1,-1,maxdist);
37             while(m--){
38                 scanf("%d",&k);
39                 if(k<=maxdist)printf("%d\n",k-1);
40                 else printf("%d\n",maxdist+(k-maxdist-1)*2);
41             }
42         }
43     }
44     return 0;
45 }