Submission #895566

#	Time	Username	Problem	Language	Result	Execution time	Memory
895566		Hando	Cat in a tree (BOI17_catinatree)	C++17	100 / 100	319 ms	70616 KiB

catinatree

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

#define ar array
#define vt vector
#define pq priority_queue
#define pu push
#define pub push_back
#define em emplace
#define emb emplace_back
#define mt make_tuple

#define all(x) x.begin(), x.end()
#define allr(x) x.rbegin(), x.rend()
#define allp(x, l, r) x.begin() + l, x.begin() + r
#define len(x) (int)x.size()
#define uniq(x) unique(all(x)), x.end()

using ll = long long;
using ld = long double;
using ull = unsigned long long;

template<class Fun> class y_combinator_result {
    Fun fun_;
public:
    template<class T> explicit y_combinator_result(T &&fun): fun_(std::forward<T>(fun)) {}
    template<class ...Args> decltype(auto) operator()(Args &&...args) { return fun_(std::ref(*this), std::forward<Args>(args)...); }
};
template<class Fun> decltype(auto) y_combinator(Fun &&fun) { return y_combinator_result<std::decay_t<Fun>>(std::forward<Fun>(fun)); }

template <class T, size_t N>
void re(array <T, N>& x);
template <class T> 
void re(vt <T>& x);

template <class T> 
void re(T& x) {
    cin >> x;
}

template <class T, class... M> 
void re(T& x, M&... args) {
    re(x), re(args...);
}

template <class T> 
void re(vt <T>& x) {
    for(auto& it : x) re(it);
}

template <class T, size_t N>
void re(array <T, N>& x) {
    for(auto& it : x) re(it);
}

template <class T, size_t N>
void wr(const array <T, N>& x);
template <class T> 
void wr(const vt <T>& x);

template <class T> 
void wr(const T& x) {
    cout << x;
}

template <class T, class ...M>  
void wr(const T& x, const M&... args) {
    wr(x), wr(args...);
}

template <class T> 
void wr(const vt <T>& x) {
    for(auto it : x) wr(it, ' ');
}

template <class T, size_t N>
void wr(const array <T, N>& x) {
    for(auto it : x) wr(it, ' ');
}

template<class T, class... M>
auto mvt(size_t n, M&&... args) {
    if constexpr(sizeof...(args) == 1)
        return vector<T>(n, args...);
    else
        return vector(n, mvt<T>(args...));
}

void set_fixed(int p = 0) {
    cout << fixed << setprecision(p);
}

void set_scientific() {
    cout << scientific;
}

void Open(const string& name) {
#ifndef ONLINE_JUDGE
    (void)!freopen((name + ".in").c_str(), "r", stdin);
    (void)!freopen((name + ".out").c_str(), "w", stdout);
#endif
}

const int inf = 1e9;

void solve() {
    int n, k; re(n, k);
    vt <vt <int>> adj(n);
    for (int v = 1; v < n; ++v) {
        int u; re(u);
        adj[u].emb(v);
        adj[v].emb(u);
    }

    set <ar <int, 2>> ans;
    vt <set <ar <int, 2>>> s(n);
    for (int u = 0; u < n; ++u)
        s[u].insert({inf, -1});

    auto df = y_combinator([&](auto&& df, int u, int p = -1, int depth = 0) -> void {
        s[u].insert({depth, u});
        for (auto& v : adj[u]) {
            if (v == p)
                continue;
            df(v, u, depth + 1);

            auto b = s[u].begin();
            auto a = b; ++b;
            auto d = s[v].begin();
            auto c = d; ++d;

            if ((*a)[0] + (*c)[0] - 2 * depth < k) {
                if ((*c)[0] > (*a)[0])
                    s[u].erase(a);
                else
                    s[v].erase(c);
            }

            if (len(s[u]) < len(s[v]))
                swap(s[u], s[v]);

            for (auto& x : s[v])
                s[u].insert(x);
        }

        if (len(ans) < len(s[u]))
            ans = s[u];
    });

    df(0);


    vt <int> res;
    for (auto& [d, u] : ans) {
        if (d != inf)
            res.emb(u + 1);
    }

    wr(len(res));
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    //Open("");

    int t = 1;
    for(;t;t--) {
        solve();
    }
    
    return 0;
}

• Subtask 1: 11 / 11
• Subtask 2: 40 / 40
• Subtask 3: 49 / 49