Submission #827482

#	Time	Username	Problem	Language	Result	Execution time	Memory
827482		BERNARB01	Newspapers (CEOI21_newspapers)	C++17	54 / 100	1 ms	468 KiB

newspapers

/**
 *    author:  BERNARD B.01
**/
#include <bits/stdc++.h>

using namespace std;

#ifdef B01
#include "deb.h"
#else
#define deb(...)
#endif

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, m;
  cin >> n >> m;
  if (m != n - 1) {
    cout << "NO" << '\n';
    return 0;
  }
  vector<vector<int>> g(n);
  for (int i = 0; i < m; i++) {
    int u, v;
    cin >> u >> v;
    --u; --v;
    g[u].push_back(v);
    g[v].push_back(u);
  }
  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 << '\n';
    cout << 1 << '\n';
    return 0;
  }
  int d = 0, to = 0;
  function<void(int, int, int)> Dfs = [&](int v, int pr, int dph) {
    if (dph >= d) {
      d = dph;
      to = v;
    }
    for (int u : g[v]) {
      if (u == pr) {
        continue;
      }
      Dfs(u, v, dph + 1);
    }
  };
  Dfs(0, -1, 0);
  int a = to;
  Dfs(to, -1, 0);
  int b = to;
  vector<int> que;
  vector<int> dist(n, -1);
  function<bool(int, int, int)> Mark = [&](int v, int pr, int tar) {
    if (v == tar) {
      que.push_back(v);
      dist[v] = 0;
      return true;
    }
    for (int u : g[v]) {
      if (u == pr) {
        continue;
      }
      if (Mark(u, v, tar)) {
        que.push_back(v);
        dist[v] = 0;
        return true;
      }
    }
    return false;
  };
  Mark(a, -1, b);
  for (int b = 0; b < (int) que.size(); b++) {
    for (int u : g[que[b]]) {
      if (dist[u] == -1) {
        dist[u] = dist[que[b]] + 1;
        que.push_back(u);
      }
    }
  }
  if (*max_element(dist.begin(), dist.end()) > 2) {
    cout << "NO" << '\n';
    return 0;
  }
  vector<int> z;
  function<void(int, int)> Dfs2 = [&](int v, int pr) {
    if (g[v].size() > 1) {
      z.push_back(v);
    }
    bool bl = false;
    for (int u : g[v]) {
      if (u == pr) {
        continue;
      }
      Dfs2(u, v);
      if (g[v].size() > 1 && g[u].size() > 1) {
        z.push_back(v);
      } else if (g[v].size() > 1 && g[u].size() == 1) {
        bl = true;
      }
    }
    if (bl) {
      z.push_back(v);
    }
  };
  for (int i = 0; i < n; i++) {
    if (g[i].size() == 1) {
      Dfs2(i, -1);
      break;
    }
  }
  cout << "YES" << '\n';
  cout << (int) z.size() << '\n';
  for (int i = 0; i < (int) z.size(); i++) {
    if (i > 0) {
      cout << " ";
    }
    cout << z[i] + 1;
  }
  cout << '\n';
  return 0;
}

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