Language: C++

#include <bits/stdc++.h>
#include <random>

using namespace std;

typedef unsigned long long ull;
typedef long long ll;
typedef long double ld;
#define int ll
//#define int unsigned __int128
//#define ll unsigned __int128
typedef pair<int, int   > pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector< vi > vvi;
typedef vector< vvi > vvvi;
typedef vector<short> vs;
typedef vector<vs> vvs;
typedef vector<vvs> vvvs;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
typedef vector<ld> vld;
typedef vector<vld> vvld;
typedef vector<vvld> vvvld;
typedef vector<string> vst;
typedef vector<vst> vvst;
typedef pair<ld, ld> pld;
typedef complex<double> base;

#define inmin(a, b) a = min(a, (b))
#define inmax(a, b) a = max(a, (b))
#define ALL(a) a.begin(),a.end()
#define RALL(a) a.rbegin(),a.rend()
#define sqr(x) ((x) * (x))
#define fori(i, n) for(int i = 0; i < (int)(n); ++i)
#define SZ(a) ((int)((a).size()))
#define triple(T) tuple<T, T, T>
#define quad(T) tuple<T, T, T, T>
#define watch(x) cerr << (#x) << " = " << (x) << endl;

#ifdef RUS_HOME
#define cerr cout
#else
#define cerr if (false) cerr
#endif

const double PI = 2 * acos(0.0);

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rng_64(chrono::steady_clock::now().time_since_epoch().count());

const string DIGITS = "0123456789";
const string ALPH = "abcdefghijklmnopqrstuvwxyz";

template <class T0, class T1>
inline ostream & operator << (ostream &out, pair<T0, T1> &a) {
    return out << "{" << a.first << ", " << a.second << "}";
}

template <class T0, class T1, class T2>
inline ostream & operator << (ostream &out, tuple<T0, T1, T2> &a) {
    return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a) << "}";
}

template <class T0, class T1, class T2, class T3>
inline ostream & operator << (ostream &out, tuple<T0, T1, T2, T3> &a) {
    return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a) << ", " <<  get<3>(a) << "}";
}

template<class T>
inline ostream & operator << (ostream &out, vector<T> &a) {
    out << "[";
    fori (i, a.size())
        out << a[i] << vector<string>{", ", "]  "}[i + 1 == a.size()];
    return out;
}



void smain();

signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

#ifdef RUS_HOME
    freopen("input.txt", "r", stdin);
    clock_t start = clock();
#else
    //freopen("dictionary.in", "r", stdin);
    //freopen("dictionary.out", "w", stdout);
#endif
    cout << setprecision(12) << fixed;
    smain();
#ifdef RUS_HOME
    cout << "\n\n\n\nTOTAL EXECUTION TIME: " << float( clock () - start ) /  CLOCKS_PER_SEC << endl;
#endif
    return 0;
}

const int N = 2e3 + 100, oo = 1e9;

vi g[N];
vector <bool> us(N);
vi nm(N);
multiset <int> st[N];
int n, k;

void dfs(int v) {
    st[v].insert(0);

    set <pii> s;
    for (int i = 0; i < g[v].size(); i++) {
        int to = g[v][i];
        if (!us[to]) {
            us[to] = true;
            nm[to] = v;
            dfs(to);
            if (st[to].size()) {
                auto it = st[to].end();
                it--;
                s.insert({*it, to});
            }
        }
    }

    while (s.size() >= 2) {
        auto it = s.end(); it--;
        auto p1 = *it;
        it--;
        auto p2 = *it;

        if (p1.first + p2.first + 2 > k) {
            auto it2 = st[p1.second].end();
            it2--;
            st[p1.second].erase(it2);
            s.erase(p1);
            if (st[p1.second].size()) {
                it2 = st[p1.second].end();
                it2--;
                s.insert({*it2, p1.second});
            }
        } else
            break;
    }

    for (int i = 0; i < g[v].size(); i++) {
        int to = g[v][i];
        if (nm[to] == v) {
            for (auto p : st[to]) {
                if (p < k - 1) {
                    st[v].insert(p + 1);
                }
            }
            st[to].clear();
        }
    }



}

void smain() {

    cin >> n >> k;
    for (int i = 0; i < n - 1; i++) {
        int a, b;
        cin >> a >> b;
        g[a].push_back(b);
        g[b].push_back(a);
    }

    int ans = oo;

    for (int i = 1; i <= n; i++) {
        us[i] = true;
        dfs(i);
        ans = min(ans, n - st[i].size());
        st[i].clear();
        fill(ALL(us), 0);
        fill(ALL(nm), 0);
    }

    cout << ans;

}

Compiler output:
a.cc: In function 'void smain()':
a.cc:179:18: error: no matching function for call to 'min(ll&, long long unsigned int)'
  179 |         ans = min(ans, n - st[i].size());
      |               ~~~^~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_algobase.h:233:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::min(const _Tp&, const _Tp&)'
  233 |     min(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:233:5: note:   template argument deduction/substitution failed:
a.cc:179:18: note:   deduced conflicting types for parameter 'const _Tp' ('long long int' and 'long long unsigned int')
  179 |         ans = min(ans, n - st[i].size());
      |               ~~~^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:281:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::min(const _Tp&, const _Tp&, _Compare)'
  281 |     min(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:281:5: note:   candidate expects 3 arguments, 2 provided
In file included from /usr/include/c++/14/algorithm:61:
/usr/include/c++/14/bits/stl_algo.h:5686:5: note: candidate: 'template<class _Tp> constexpr _Tp std::min(initializer_list<_Tp>)'
 5686 |     min(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5686:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5696:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::min(initializer_list<_Tp>, _Compare)'
 5696 |     min(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5696:5: note:   template argument deduction/substitution failed:
a.cc:179:18: note:   mismatched types 'std::initializer_list<_Tp>' and 'long long int'
  179 |         ans = min(ans, n - st[i].size());
      |               ~~~^~~~~~~~~~~~~~~~~~~~~~~