Pet(dfs)

http://acm.hdu.edu.cn/showproblem.php?pid=4707

题意：判断距离大于D的点有多少个。

思路: 邻接表建图，dfs每一个点，记录步数。

 #include <stdio.h>
 #include <string.h>
 const int N=;
 int vis[N],dis[N],head[N],cnt,step;
 struct node
 {
     int u;
     int v;
     int next;
 } edge[N];
 void add(int u,int v)
 {
     edge[cnt].u = u;
     edge[cnt].v = v;
     edge[cnt].next = head[u];
     head[u] = cnt++;
 };
 void dfs(int u,int step)
 {
     if (vis[u])
         return ;
     dis[u] = step;
     vis[u] = ;
     for (int j = head[u]; j != -; j = edge[j].next)
     {
         int v = edge[j].v;
         if (!vis[v])
         {
             dfs(v,step+);
         }
     }
     return ;
 }
 void init()
 {
     memset(head,-,sizeof(head));
     memset(vis,,sizeof(vis));
     cnt = ;

 }
 int main()
 {
     int t,n,d,u,v;
     scanf("%d",&t);
     while(t--)
     {
         scanf("%d%d",&n,&d);
         init();
         for (int i = ; i < n; i ++)
         {
             scanf("%d%d",&u,&v);
             add(u,v);
             add(v,u);
         }
         dfs(,);
         int ans = ;
         for (int i = ; i < n; i ++)
         {
             if (dis[i] > d)
                 ans++;
         }
         printf("%d\n",ans);
     }
     return ;
 }