```cpp
#include<iostream>
#include<cstring>
#include<queue>
using namespace std;
const int N = 1e5 + 10;
int h[N], e[N], ne[N], idx, n, d,res;
bool f[N];
queue<int> que;
void connec(int x, int y)
{
e[idx] = y;
ne[idx] = h[x];
h[x] = idx++;
return;
}
void dfs(int cur,int v)
{
if (v == d||f[cur]) return;
f[cur] = 1;
for (int i = h[cur]; i != -1; i = ne[i]) {
int index_ = e[i];
if (f[index_] == 0)res++, dfs(index_, v +1);
}
return;
}
int main()
{
memset(h, -1, sizeof h);
cin >> n >> d;
for (int i = 1; i < n; i++) {
int x, y;
cin >> x >> y;
connec(x, y);
connec(y, x);
}
if (d == 0) { cout << 0 << endl; return 0; }
dfs(1,0);
cout << res << endl;
return 0;
}
```
我的dfs20分做法
by Man_CCNU @ 2021-12-07 16:00:18