Uva 网络(Network,Seoul 2007,LA 3902)

 #include<iostream>
 #include<cstring>
 #include<vector>
 using namespace std;

 const int maxn=+;
 int n,s,k;
 vector<int> tree[maxn],nodes[maxn];
 int fa[maxn];
 bool covered[maxn];

 void dfs(int u,int f,int d)
 {
     fa[u]=f;
     int nc=tree[u].size();
     if(nc==&&d>k) nodes[d].push_back(u);
     for(int i=;i<nc;i++)
         if(tree[u][i]!=f) dfs(tree[u][i],u,d+);
 }

 void dfs2(int u,int f,int d)
 {
     int nc=tree[u].size();
     covered[u]=true;
     for(int i=;i<nc;i++)
         if(tree[u][i]!=f&&d<k)
             dfs2(tree[u][i],u,d+);
 }

 int solve()
 {
     int ans=;
     memset(covered,,sizeof(covered));
     for(int d=n-;d>k;d--)
         for(int i=;i<nodes[d].size();i++)
         {
             int u=nodes[d][i];
             if(covered[u]) continue;
             int v=u;
             for(int j=;j<k;j++) v=fa[v];
             dfs2(v,-,);
             ans++;
         }
     return ans;
 }

 int main()
 {
     int T;
     cin>>T;
     while(T--)
     {
         cin>>n>>s>>k;
         for(int i=;i<=n;i++)
         {
             tree[i].clear();
             nodes[i].clear();
         }
         for(int i=;i<=n-;i++)
         {
             int a,b;
             cin>>a>>b;
             tree[a].push_back(b);
             tree[b].push_back(a);
         }
         dfs(s,-,);
         cout<<solve()<<endl;
     }
     return ;
 }