Submission #518619

#	Time	Username	Problem	Language	Result	Execution time	Memory
518619		prvocislo	Newspapers (CEOI21_newspapers)	C++17	100 / 100	1 ms	460 KiB

newspapers

#include <algorithm>
#include <iostream>
#include <string>
#include <vector>
#include <set>
#include <map>
#include <queue>
typedef long long ll;
using namespace std;

const int maxn = 1e3 + 5;
vector<vector<int> > g;
vector<int> d, p;
int n, m;
void ready()
{
    d.assign(n, -1), p.assign(n, -1);
}
void dfs(int u)
{
    for (int v : g[u])
    {
        if (d[v] == -1)
        {
            d[v] = d[u] + 1;
            p[v] = u;
            dfs(v);
        }
    }
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> n >> m;
    if (m >= n)
    {
        cout << "NO\n";
        return 0;
    }
    if (n <= 2)
    {
        cout << "YES\n" << n << "\n";
        for (int i = 0; i < n; i++) cout << "1 ";
        cout << "\n";
        return 0;
    }
    g.assign(n, {});
    for (int i = 0, a, b; i < n - 1; i++)
    {
        cin >> a >> b;
        a--, b--;
        g[a].push_back(b);
        g[b].push_back(a);
    }
    ready();
    d[0] = 0;
    dfs(0);
    int e1 = max_element(d.begin(), d.end()) - d.begin();
    ready();
    d[e1] = 0;
    dfs(e1);
    int e2 = max_element(d.begin(), d.end()) - d.begin();
    vector<int> di;
    for (int i = e2; i != -1; i = p[i]) di.push_back(i);
    ready();
    for (int i : di) d[i] = 0;
    for (int i : di) dfs(i);
    if (*max_element(d.begin(), d.end()) >= 3)
    {
        cout << "NO\n";
        return 0;
    }
    cout << "YES\n";
    vector<int> ans;
    for (int i = 1; i + 1 < di.size(); i++)
    {
        ans.push_back(di[i]);
        for (int j : g[di[i]]) if (d[j] && g[j].size() > 1)
        {
            ans.push_back(j);
            ans.push_back(di[i]);
        }
    }
    int k = ans.size();
    for (int i = 0; i < k; i++) ans.push_back(ans[k - i - 1]);
    cout << ans.size() << "\n";
    for (int i = 0; i < ans.size(); i++) cout << ans[i] + 1 << " \n"[i == ans.size() - 1];
    return 0;
}

Compilation message (stderr)

newspapers.cpp: In function 'int main()':
newspapers.cpp:76:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   76 |     for (int i = 1; i + 1 < di.size(); i++)
      |                     ~~~~~~^~~~~~~~~~~
newspapers.cpp:88:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   88 |     for (int i = 0; i < ans.size(); i++) cout << ans[i] + 1 << " \n"[i == ans.size() - 1];
      |                     ~~^~~~~~~~~~~~
newspapers.cpp:88:72: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   88 |     for (int i = 0; i < ans.size(); i++) cout << ans[i] + 1 << " \n"[i == ans.size() - 1];
      |                                                                      ~~^~~~~~~~~~~~~~~~~

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