Language: C++

#include<bits/stdc++.h>
using namespace std;
const int MAXN=4000+5;
int first[MAXN*2],next[MAXN*2],get[MAXN*2],have1,have2;
int deep[MAXN],fa[MAXN],have[MAXN];
int n,k,top,ans,now,kkk,maxkkk;
inline void add(int x,int y){get[++top]=y;next[top]=first[x];first[x]=top;}
void dfs(int x,int f,int d){
	deep[x]=d; fa[x]=f; if (deep[x]>k/2) ++now;
	for (int i=first[x];i;i=next[i]){
		int v=get[i];
		if (v==f) continue;
		dfs(v,x,d+1);
	}
}
void dfs1(int x,int f,int d){
	deep[x]=d; fa[x]=f; if (deep[x]>k/2) ++now;
	for (int i=first[x];i;i=next[i]){
		int v=get[i];
		if (v==f) continue;
		dfs1(v,x,d+1);
	}
}
void find(int x,int f){
	if (deep[x]==(k/2)+1) ++kkk;
	if (deep[x]>=(k/2)+1) return;
	for (int i=first[x];i;i=next[i]){
		int v=get[i];
		if (v==f) continue;
		find(v,x);
	}
}
int main(){
	//freopen(".in","r",stdin);
	scanf("%d%d",&n,&k); ans=n;
	if (k>=n){
		printf("0"); return 0;
	}
	int x,y;
	for (int i=1;i<n;++i){
		scanf("%d%d",&x,&y);
		add(x,y);add(y,x); ++have[x]; ++have[y];
	}
	for (int i=1;i<=n;++i){
		if (have[i]==1) ++have1;
		if (have[i]==2) ++have2;
	}
	if (have1==2&&have2==(n-2)){
		printf("%d",max(0,n-k));
		return 0;
	}
	if (k%2==1){
		for (int i=1;i<=n;++i){
			memset(deep,0,sizeof(deep)); now=0;
			dfs1(i,0,0); maxkkk=0;
			for (int j=first[i];j;j=next[j]){
				kkk=0;
				find(get[j],i);
				maxkkk=max(maxkkk,kkk);
			}
			ans=min(ans,now-maxkkk);
		}
		printf("%d",ans-1);
		return 0;
	} else {
		for (int i=1;i<=n;++i){
			memset(deep,0,sizeof(deep)); now=0;
			dfs(i,0,0);
			ans=min(ans,now);
		}
		printf("%d",ans);
		return 0;
	}
}

Compiler output:
a.cc: In function 'void add(int, int)':
a.cc:7:30: error: reference to 'get' is ambiguous
    7 | inline void add(int x,int y){get[++top]=y;next[top]=first[x];first[x]=top;}
      |                              ^~~
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:80,
                 from a.cc:1:
/usr/include/c++/14/variant:1180:5: note: candidates are: 'template<class _Tp, class ... _Types> constexpr const _Tp&& std::get(const variant<_Types ...>&&)'
 1180 |     get(const variant<_Types...>&& __v)
      |     ^~~
/usr/include/c++/14/variant:1170:5: note:                 'template<class _Tp, class ... _Types> constexpr const _Tp& std::get(const variant<_Types ...>&)'
 1170 |     get(const variant<_Types...>& __v)
      |     ^~~
/usr/include/c++/14/variant:1160:5: note:                 'template<class _Tp, class ... _Types> constexpr _Tp&& std::get(variant<_Types ...>&&)'
 1160 |     get(variant<_Types...>&& __v)
      |     ^~~
/usr/include/c++/14/variant:1150:5: note:                 'template<class _Tp, class ... _Types> constexpr _Tp& std::get(variant<_Types ...>&)'
 1150 |     get(variant<_Types...>& __v)
      |     ^~~
/usr/include/c++/14/variant:1748:5: note:                 'template<long unsigned int _Np, class ... _Types> constexpr std::variant_alternative_t<_Np, std::variant<_Types ...> >&& std::get(const variant<_Types ...>&&)'
 1748 |     get(const variant<_Types...>&& __v)
      |     ^~~
/usr/include/c++/14/variant:1737:5: note:                 'template<long unsigned int _Np, class ... _Types> constexpr std::variant_alternative_t<_Np, std::variant<_Types ...> >& std::get(const variant<_Types ...>&)'
 1737 |     get(const variant<_Types...>& __v)
      |     ^~~
/usr/include/c++/14/variant:1726:5: note:                 'template<long unsigned int _Np, class ... _Types> constexpr std::variant_alternative_t<_Np, std::variant<_Types ...> >&& std::get(variant<_Types ...>&&)'
 1726 |     get(variant<_Types...>&& __v)
      |     ^~~
/usr/include/c++/14/variant:1715:5: note:                 'template<long unsigned int _Np, class ... _Types> constexpr std::variant_alternative_t<_Np, std::variant<_Types ...> >& std::get(variant<_Types ...>&)'
 1715 |     get(variant<_Types...>& __v)
      |     ^~~
In file included from /usr/include/c++/14/bits/memory_resource.h:47,
                 from /usr/include/c++/14/string:68,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/usr/include/c++/14/tuple:2517:5: note:                 'template<class _Tp, class ... _Types> constexpr const _Tp&& std::get(const tuple<_Elements ...>&&)'
 2517 |     get(const tuple<_Types...>&& __t) noexcept
      |     ^~~
/usr/include/c++/14/tuple:2505:5: note:                 'template<class _Tp, class ... _Types> constexpr const _Tp& std::get(const tuple<_Elements ...>&)'
 2505 |     get(const tuple<_Types...>& __t) noexcept
      |     ^~~
/usr/include/c++/14/tuple:2494:5: note:                 'template<class _Tp, class ... _Types> constexpr _Tp&& std::get(tuple<_Elements ...>&&)'
 2494 |     get(tuple<_Types...>&& __t) noexcept
      |     ^~~
/usr/include/c++/14/tuple:2483:5: note:                 'template<class _Tp, class ... _Types> constexpr _Tp& std::get(tuple<_Elements ...>&)'
 2483 |     get(tuple<_Types...>& __t) noexcept
      |     ^~~
/usr/include/c++/14/tuple:2476:5: note:                 'template<long unsigned int __i, class ... _Elements> constexpr std::__enable_if_t<(__i >= sizeof... (_Types))> std::get(const tuple<_Elements ...>&)'
 2476 |     get(const tuple<_Elements...>&) = delete;
      |     ^~~
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51:
/usr/include/c++/14/bits/stl_pair.h:1307:5: note:                 'template<class _Tp, class _Up> constexpr const _Tp&& std::get(const pair<_Up, _Tp>&&)'
 1307 |     get(const pair<_Up, _Tp>&& __p) noexcept
      |     ^~~
/usr/include/c++/14/bits/stl_pair.h:1302:5: note:                 'template<class _Tp, class _Up> constexpr _Tp&& std::get(pair<_Up, _Tp>&&)'
 1302 |     get(pair<_Up, _Tp>&& __p) noexcept
      |     ^~~
/usr/include/c++/14/bits/stl_pair.h:1297:5: note:                 'template<class _Tp, class _Up> constexpr const _Tp& std::get(const pair<_Up, _Tp>&)'
 1297 |     get(const pair<_Up, _Tp>& __p) noexcept
      |     ^~~
/usr/include/c++/14/bits/stl_pair.h:1292:5: note:                 'template<class _Tp, class _Up> constexpr _Tp& std::get(pair<_Up, _Tp>&)'
 1292 |     get(pair<_Up, _Tp>& __p) noexcept
      |     ^~~
/usr/include/c++/14/bits/stl_pair.h:1287:5: note:                 'template<class _Tp, class _Up> constexpr const _Tp&& std::get(const pair<_T1, _T2>&&)'
 1287 |     get(const pair<_Tp, _Up>&& __p) noexcept
      |     ^~~
/usr/include/c++/14/bits/stl_pair.h:1282:5: note:                 'template<class _Tp, class _Up> constexpr _Tp&& std::get(pair<_T1, _T2>&&)'
 1282 |     get(pair<_Tp, _Up>&& __p) noexcept
      |     ^~~
/usr/include/c++/14/bits/stl_pair.h:1277:5: note:                 'template<class _Tp, class _Up> constexpr const _Tp& std::get(const pair<_T1, _T2>&)'
 1277 |     get(const pair<_Tp, _Up>& __p) noexcept
      |     ^~~
/usr/include/c++/14/bits/stl_pair.h:1272:5: note:                 'template<class _Tp, class _Up> constexpr _Tp& std::get(pair<_T1, _T2>&)'
 1272 |     get(pair<_Tp, _Up>& __p) noexcept
      |     ^~~
In file included from /usr/include/c++/14/functional:65,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:53:
/usr/include/c++/14/array:417:5: note:                 'template<long unsigned int _Int, class _Tp, long unsigned int _Nm> constexpr const _Tp&& std::get(const array<_Tp, _Nm>&&)'
  417 |     get(const array<_Tp, _Nm>&& __arr) noexcept
      |     ^~~
/usr/include/c++/14/array:408:5: note:                 'template<long unsigned int _Int, class _Tp, long unsigned int _Nm> constexpr const _Tp& std::get(const array<_Tp, _Nm>&)'
  408 |     get(const array<_Tp, _Nm>& __arr) noexcept
      |     ^~~
/usr/include/c++/14/array:399:5: note:                 'template<long unsigned int _Int, class _Tp, long unsigned int _Nm> constexpr _Tp&& std::get(array<_Tp, _Nm>&&)'
  399 |     get(array<_Tp, _Nm>&& __arr) noexcept
      |     ^~~
/usr/include/c++/14/array:390:5: note:                 'template<long unsigned int _Int, class _Tp, long unsigned int _Nm> constexpr _Tp& std::get(array<_Tp, _Nm>&)'
  390 |     get(array<_Tp, _Nm>& __arr) noexcept
      |     ^~~
/usr/include/c++/14/tuple:2466:5: note:                 'template<long unsigned int __i, class ... _Elements> constexpr std::__tuple_element_t<__i, std::tuple<_Elements ...> >&& std::get(const tuple<_Elements ...>&&)'
 2466 |     get(const tuple<_Elements...>&& __t) noexcept
      |     ^~~
/usr/include/c++/14/tuple:2457:5: note:                 'template<long unsigned int __i, class ... _Elements> constexpr std::__tuple_element_t<__i, std::tuple<_Elements ...> >&& std::get(tuple<_Elements ...>&&)'
 2457 |     get(tuple<_Elements...>&& __t) noexcept
      |     ^~~
/usr/include/c++/14/tuple:2451:5: note:                 'template<long unsigned int __i, class ... _Elements> constexpr std::__tuple_element_t<__i, std::tuple<_Elements ...> >& std::get(const tuple<_Elements ...>&)'
 2451 |     get(const tuple<_Elements...>& __t) noexcept
      |     ^~~
/usr/include/c++/14/tuple:2445:5: note:                 'template<long unsigned int __i, class ... _Elements> constexpr std::__tuple_element_t<__i, std::tuple<_Elements ...> >& std::get(tuple<_Elements ...>&)'
 2445 |     get(tuple<_Elements...>& __t) noexcept
      |     ^~~
/usr/include/c++/14/bits/stl_pair.h:1265:5: note:                 'template<long unsigned int _Int, class _Tp1, class _Tp2> constexpr const typename std::tuple_element<_Int, std::pair<_Tp1, _Tp2> >::type&& std::get(const pair<_Tp1, _Tp2>&&)'
 1265 |     get(const pair<_Tp1, _Tp2>&& __in) noexcept
      |     ^~~
/usr/include/c++/14/bits/stl_pair.h:1260:5: note:                 'template<long unsigned int _Int, class _Tp1, class _Tp2> constexpr const typename std::tuple_element<_Int, std::pair<_Tp1, _Tp2> >::type& std::get(const pair<_Tp1, _Tp2>&)'
 1260 |     get(const pair<_Tp1, _Tp2>& __in) noexcept
      |     ^~~
/usr/include/c++/14/bits/stl_pair.h:1255:5: note:                 'template<long unsigned int _Int, class _Tp1, class _Tp2> constexpr typename std::tuple_element<_Int, std::pair<_Tp1, _Tp2> >::type&& std::get(pair<_Tp1, _Tp2>&&)'
 1255 |     get(pair<_Tp1, _Tp2>&& __in) noexcept
      |     ^~~
/usr/include/c++/14/bits/stl_pair.h:1250:5: note:                 'template<long unsigned int _Int, class _Tp1, class _Tp2> constexpr typename std::tuple_element<_Int, std::pair<_Tp1, _Tp2> >::type& std::get(pair<_Tp1, _Tp2>&)'
 1250 |     get(pair<_Tp1, _Tp2>& __in) noexcept
      |     ^~~
a.cc:4:32: note:                 'int get [8010]'
    4 | int first[MAXN*2],next[MAXN*2],get[MAXN*2],have1,have2;
      |                                ^~~
a.cc:7:43: error: reference to 'next' is ambiguous
    7 | inline void add(int x,int y){get[++top]=y;next[top]=first[x];first[x]=top;}
      |                                           ^~~~
In file included from /usr/include/c++/14/bits/stl_algobase.h:66:
/usr/include/c++/14/bits/stl_iterator_base_funcs.h:232:5: note: candidates are: 'template<class _InputIterator> constexpr _InputIterator std::next(_InputIterator, typename iterator_traits<_Iter>::difference_type)'
  232 |     next(_InputIterator __x, typename
      |     ^~~~
a.cc:4:19: note:                 'int next [8010]'
    4 | int first[MAXN*2],next[MAXN*2],get[MAXN*2],have1,have2;
      |                   ^~~~
a.cc: In function 'void dfs(int, int, int)':
a.cc:10:33: error: reference to 'next' is ambiguous
   10 |         for (int i=first[x];i;i=next[i]){
      |                                 ^~~~
/usr/include/c++/14/bits/stl_iterator_base_funcs.h:232:5: note: candidates are: 'template<class _InputIterator> constexpr _InputIterator std::next(_InputIterator, typename iterator_traits<_Iter