Submission #613977

#	Time	Username	Problem	Language	Result	Execution time	Memory
613977		yuto1115	Newspapers (CEOI21_newspapers)	C++17	100 / 100	64 ms	4584 KiB

newspapers

#include <bits/stdc++.h>
#define rep(i, n) for(ll i = 0; i < ll(n); ++i)
#define rep2(i, s, n) for(ll i = ll(s); i < ll(n); ++i)
#define rrep(i, n) for(ll i = ll(n) - 1; i >= 0; --i)
#define rrep2(i, n, t) for(ll i = ll(n) - 1; i >= ll(t); --i)
#define pb push_back
#define eb emplace_back
#define all(a) a.begin(), a.end()
#define SZ(a) int(a.size())
using namespace std;
using ll = long long;
using P = pair<int, int>;
using vi = vector<int>;
using vvi = vector<vi>;
using vl = vector<ll>;
using vvl = vector<vl>;
using vp = vector<P>;
using vvp = vector<vp>;
using vb = vector<bool>;
using vvb = vector<vb>;
using vs = vector<string>;
const int inf = 1001001001;
const ll linf = 1001001001001001001;

template<class T>
bool chmin(T &a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}

template<class T>
bool chmax(T &a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

vi solve2(int n, vvi G) {
    if (n == 1) return {1};
    if (n == 2) return {1, 1};
    auto dfs = [&](auto &dfs, int u, int p) -> vi {
        vi res;
        for (int v: G[u]) {
            if (v == p) continue;
            vi now = dfs(dfs, v, u);
            if (SZ(now) > SZ(res)) res = now;
        }
        res.pb(u);
        return res;
    };
    int a = dfs(dfs, 0, -1)[0];
    vi dm = dfs(dfs, a, -1);
    vi res;
    rep2(i, 1, SZ(dm) - 1) {
        res.pb(dm[i] + 1);
        for (int j: G[dm[i]]) {
            if (j == dm[i - 1] or j == dm[i + 1]) continue;
            vi now = dfs(dfs, j, dm[i]);
            if (SZ(now) >= 3) return {};
            if (SZ(now) == 2) {
                res.pb(now.back() + 1);
                res.pb(dm[i] + 1);
            }
        }
    }
    vi rev = res;
    reverse(all(rev));
    res.insert(res.end(), all(rev));
    return res;
}

vi solve(int n, vvi G) {
    if (n == 1) return {1};
    assert(n <= 20);
    vi d(1 << n, inf);
    vp pre(1 << n);
    queue<int> q;
    d[(1 << n) - 1] = 0;
    q.push((1 << n) - 1);
    while (not q.empty()) {
        int now = q.front();
        q.pop();
        int nx = 0;
        rep(i, n) {
            for (int j: G[i]) {
                if (now >> j & 1) nx |= 1 << i;
            }
        }
        rep(i, n) {
            if (~nx >> i & 1) continue;
            nx -= 1 << i;
            if (chmin(d[nx], d[now] + 1)) {
                q.push(nx);
                pre[nx] = {now, i};
            }
            nx += 1 << i;
        }
    }
    if (d[0] == inf) return {};
    vi ans;
    int now = 0;
    while (now < (1 << n) - 1) {
        ans.pb(pre[now].second + 1);
        now = pre[now].first;
    }
    reverse(all(ans));
    return ans;
}

random_device seed_gen;
mt19937 engine(seed_gen());

int rnd(int mn, int mx) {
    uniform_int_distribution<int> dist(mn, mx);
    return dist(engine);
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr), cout.tie(nullptr);
//    int n;
//    cin >> n;
//    rep(_, 10000) {
//        vvi G(n);
//        rep2(i, 1, n) {
//            int j = rnd(0, i - 1);
//            G[i].pb(j);
//            G[j].pb(i);
//        }
//        if (solve(n, G).empty() != solve2(n, G).empty()) {
//            cout << "#" << endl;
//            rep(i, n) {
//                for (int j: G[i]) {
//                    if (i < j) {
//                        cout << i << ' ' << j << endl;
//                    }
//                }
//            }
//        }
//    }
    int n, m;
    cin >> n >> m;
    vvi G(n);
    rep(i, m) {
        int u, v;
        cin >> u >> v;
        --u, --v;
        G[u].pb(v);
        G[v].pb(u);
    }
    if (m > n - 1) {
        cout << "NO" << endl;
        return 0;
    }
    vi ans = solve2(n, G);
    if (ans.empty()) {
        cout << "NO" << endl;
        return 0;
    }
    cout << "YES" << endl;
    cout << SZ(ans) << endl;
    rep(i, SZ(ans)) cout << ans[i] << (i < SZ(ans) - 1 ? ' ' : '\n');
}

• Subtask 1: 12 / 12
• Subtask 2: 8 / 8
• Subtask 3: 80 / 80