Submission #576890

#	Time	Username	Problem	Language	Result	Execution time	Memory
576890		tengiz05	Newspapers (CEOI21_newspapers)	C++17	54 / 100	2 ms	468 KiB

newspapers

#include <bits/stdc++.h>

using namespace std;
using i64 = long long;

int main() {
    int n, m;
    cin >> n >> m;
    
    if (n == 1) {
        cout << "YES\n";
        cout << "1\n";
        cout << "1\n";
        return 0;
    }
    if (n == 2) {
        cout << "YES\n";
        cout << "2\n";
        cout << "1 1\n";
        return 0;
    }
    
    if (m >= n) {
        cout << "NO\n";
        return 0;
    }
    
    vector<vector<int>> adj(n);
    for (int i = 0; i < m; i++) {
        int u, v;
        cin >> u >> v;
        u--;
        v--;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    
    vector<int> dep(n);
    
    pair<int, int> mx{-1, -1};
    
    function<void(int, int)> dfs = [&](int u, int p) {
        mx = max(mx, pair(dep[u], u));
        for (int v : adj[u]) {
            if (v != p) {
                dep[v] = dep[u] + 1;
                dfs(v, u);
            }
        }
    };
    
    dfs(0, -1);
    
    int last = mx.second;
    
    mx = {-1, -1};
    dep[last] = 0;
    dfs(last, -1);
    
    int u = mx.second;
    
    vector<int> g;
    function<bool(int, int)> dfs2 = [&](int u, int p) {
        if (u == last) {
            g.push_back(u);
            return true;
        }
        for (int v : adj[u]) {
            if (v != p && dfs2(v, u)) {
                g.push_back(u);
                return true;
            }
        }
        return false;
    };
    
    dfs2(u, -1);
    
    int p = g.size() / 2;
    u = g[p];
    int l = -1, r = -1;
    if (p > 0) {
        l = g[p - 1];
    }
    if (p < int(g.size()) - 1) {
        r = g[p + 1];
    }
    
    vector<int> mxdep(n), par(n);
    dfs = [&](int u, int p) {
        par[u] = p;
        mxdep[u] = u;
        for (int v : adj[u]) {
            if (v != p) {
                dep[v] = dep[u] + 1;
                dfs(v, u);
                if (dep[mxdep[v]] > dep[mxdep[u]]) {
                    mxdep[u] = mxdep[v];
                }
            }
        }
    };
    
    dep[u] = 0;
    dfs(u, -1);
    
    for (int i = 0; i < n; i++) {
        int c = 0;
        for (int v : adj[i]) {
            if (dep[mxdep[v]] - dep[i] >= 3) {
                c++;
            }
        }
        if (c >= 3) {
            cout << "NO\n";
            return 0;
        }
    }
    
    std::vector<int> a;
    
    int s = -1;
    
    dfs = [&](int u, int p) {
        for (int v : adj[u]) {
            if (v != p && adj[v].size() > 1) {
                dfs(v, u);
            }
        }
        if (s == -1) {
            s = u;
        }
    };
    
    for (int &v : adj[u]) {
        if (v == l) {
            swap(v, adj[u][0]);
        }
        if (v == r) {
            swap(v, adj[u].back());
        }
    }
    
    dfs(u, -1);
    
    int lst = -1;
    
    dfs = [&](int u, int p) {
        a.push_back(u);
        lst = u;
        for (int v : adj[u]) {
            if (v != p && adj[v].size() > 1) {
                dfs(v, u);
                a.push_back(u);
            }
        }
    };
    
    dfs(s, -1);
    
    while (a.back() != lst)
        a.pop_back();
    
    cout << "YES\n";
    cout << 2 * a.size() << "\n";
    for (int x : a) {
        cout << x + 1 << " ";
    }
    reverse(a.begin(), a.end());
    for (int x : a) {
        cout << x + 1 << " ";
    }
    cout << "\n";
}

• Subtask 1: 6 / 12
• Subtask 2: 8 / 8
• Subtask 3: 40 / 80