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 ;

 }