```cpp
#include<bits/stdc++.h>
using namespace std;
#define long long ll
const int MAXN=1e5+10;
int n,d;
struct edge
{
int u,v;
int nxt;
} edges[200010];
int cnt=0,head[200010];
int sum=0;
bool vis[200010];
void add(int u,int v)
{
edges[++cnt].u=u;
edges[cnt].v=v;
edges[cnt].nxt=head[u];
head[u]=cnt;
}
void dfs(int u,int step)
{
if(step>d)
{
return;
}
for(int i=head[u]; i; i=edges[i].nxt)
{
if(!vis[edges[i].v])
{
sum++;
vis[edges[i].v]=1;
dfs(edges[i].v,step+1);
}
}
return;
}
int main()
{
cin>>n>>d;
for(int i=1; i<n; i++)
{
int u,v;
cin>>u>>v;
add(u,v);
}
dfs(1,1);
cout<<sum<<endl;
return 0;
}
```
还是错的↑
by yimengxiao @ 2023-06-30 21:36:15
@[yimengxiao](/user/238361) 两个问题
1. 没有双向建边
1. 一开始没有标记 $1$ 被走过，回走回去
by VIOLET__FOREVER @ 2023-08-31 20:48:31
@[yimengxiao](/user/238361) 如果觉得我说的还不错的话，可否给个关注呀
by VIOLET__FOREVER @ 2023-08-31 20:49:02
@[VIOLET__FOREVER](/user/422387) 感谢orz
by yimengxiao @ 2023-09-02 20:11:11