Submission #760304

#	Time	Username	Problem	Language	Result	Execution time	Memory
760304		Sam_a17	Newspapers (CEOI21_newspapers)	C++17	52 / 100	103 ms	596 KiB

newspapers

///
#define _CRT_SECURE_NO_WARNINGS
#include <bits/stdc++.h>
//#include "temp.cpp"
#include <cstdio>
using namespace std;
 
#ifndef ONLINE_JUDGE
#define dbg(x) cerr << #x <<" "; print(x); cerr << endl;
#else
#define dbg(x)
#endif
 
#define sz(x) (int)x.size()
#define len(x) (int)x.length()
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define clr(x) (x).clear()
#define uniq(x) x.resize(unique(all(x)) - x.begin());
#define blt __builtin_popcount
 
#define pb push_back
#define popf pop_front
#define popb pop_back
#define ld long double
 
void print(long long t) {cerr << t;}
void print(int t) {cerr << t;}
void print(string t) {cerr << t;}
void print(char t) {cerr << t;}
void print(double t) {cerr << t;}
void print(long double t) {cerr << t;}
void print(unsigned long long t) {cerr << t;}
 
template <class T, class V> void print(pair <T, V> p);
template <class T> void print(vector <T> v);
template <class T> void print(set <T> v);
template <class T, class V> void print(map <T, V> v);
template <class T> void print(multiset <T> v);
template <class T, class V> void print(T v[],V n) {cerr << "["; for(int i = 0; i < n; i++) {print(v[i]); cerr << " "; } cerr << "]";}
template <class T, class V> void print(pair <T, V> p) {cerr << "{"; print(p.first); cerr << ","; print(p.second); cerr << "}";}
template <class T> void print(vector <T> v) {cerr << "[ "; for (T i : v) {print(i); cerr << " ";} cerr << "]";}
template <class T> void print(set <T> v) {cerr << "[ "; for (T i : v) {print(i); cerr << " ";} cerr << "]";}
template <class T> void print(multiset <T> v) {cerr << "[ "; for (T i : v) {print(i); cerr << " ";} cerr << "]";}
template <class T, class V> void print(map <T, V> v) {cerr << "[ "; for (auto i : v) {print(i); cerr << " ";} cerr << "]";}
template <class T> void print(deque <T> v) {cerr << "[ "; for (T i : v) {print(i); cerr << " ";} cerr << "]";}
 
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
#define nl '\n'
 
// for random generations
// mt19937 myrand(chrono::steady_clock::now().time_since_epoch().count());
mt19937 myrand(373);
 
// for grid problems
int dx[8] = {-1,0,1,0,1,-1,1,-1};
int dy[8] = {0,1,0,-1,1,1,-1,-1};
 
// lowest / (1 << 17) >= 1e5 / (1 << 18) >= 2e5 / (1 << 21) >= 1e6
void fastIO() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr); cout.tie(nullptr);
}
// file in/out
void setIO(string str = "") {
  fastIO();
 
  if(str == "input") {
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
  } else {
    // freopen("skis.in", "r", stdin);
    // freopen("skis.out", "w", stdout);
  }
}
// Indexed Set  
template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
const int N = 1005;
vector<int> adj[N];
int vis[N];
int n, m, dp[N];
int oki = 1;

void dfs1(int node, int parent) {
  dp[node] = 1;
  int ci = 0;
  for(auto i: adj[node]) {
    if(i == parent) continue;
    dfs1(i, node);
    dp[node] = max(dp[node], dp[i] + 1);
  }
}

void dfs2(int node, int parent, int up = 0) {
  multiset<int> mt;
  int ci = 0;
  if(up >= 3) {
    ci++;
  }
  for(auto i: adj[node]) {
    if(i == parent) continue;
    mt.insert(dp[i]);
    if(dp[i] >= 3) {
      ci++;
    }
  }

  if(ci >= 3) {
    oki = 0;
  }

  for(auto i: adj[node]) {
    if(i == parent) continue;
    mt.erase(mt.find(dp[i]));
    if(mt.empty()) {
      dfs2(i, node, up + 1);
    } else {
      dfs2(i, node, max(up + 1, *mt.rbegin() + 1));
    }
    mt.insert(dp[i]);
  }
}

vector<int> ord;
void dfs_con(int node, int parent) {
  ord.push_back(node);

  multiset<pair<int, int>> mt;
  for(auto i: adj[node]) {
    if(i == parent) continue;
    mt.insert({dp[i], i});
  }
  if(!mt.empty()) {
    dfs_con(mt.rbegin()->second, node);
    ord.push_back(node);
    mt.erase(prev(mt.end()));
  }

  for(auto i: mt) {
    if(i.first == 1) continue;
    dfs_con(i.second, node);
    ord.push_back(node);
  }
}
 
void solve_() {
  cin >> n >> m;
 
  if(m > n - 1) {
    cout << "NO" << endl;
    exit(0);
  }

  int ok = 1, g = -1;
  if(m != n - 1) {
    ok = 0;
  }
 
  vector<int> deg(n + 1);
  for(int i = 1; i <= m; i++) {
    int a, b; cin >> a >> b;
    adj[a].push_back(b);
    adj[b].push_back(a);
    if(a > b) {
      swap(a, b);
    }
    if(ok && b != (a + 1)) {
      ok = 0;
    }
    deg[a]++, deg[b]++;
    if(deg[a] >= 2) {
      g = a;
    }
    if(deg[b] >= 2) {
      g = a;
    }
  }

  if(n == 1) {
    cout << "YES" << '\n';
    cout << 1 << '\n';
    cout << 1 << '\n';
    return;
  } else if(n == 2) {
    cout << "YES" << '\n';
    cout << 2 << '\n';
    cout << 1 << " " << 1 << '\n'; 
    return;
  } else if(n == 3) {
    cout << "YES" << '\n';
    cout << 2 << '\n';
    cout << g << " " << g << '\n'; 
    return;
  }

  int ok2 = 0;
  for(int i = 1; i <= n; i++) {
    oki = 1;
    dfs1(i, 0);
    dfs2(i, 0);

    if(oki) {
      ok2 = 1;
      dfs_con(i, 0);

      cout << "YES" << '\n';
      cout << 2 * sz(ord) << '\n';
      for(auto j: ord) {
        cout << j << " ";
      }
      
      for(auto j: ord) {
        cout << j << " ";
      }
      return;
    }
  }

  if(!ok2) {
    cout << "NO" << '\n';
    exit(0);
  }

}
 
int main() {
  setIO();
 
  auto solve = [&](int test_case)-> void {
    for(int i = 1; i <= test_case; i++) {
      solve_();
    }
  };
 
  int test_cases = 1;
  // cin >> test_cases;
  solve(test_cases);
 
  return 0;
} 

Compilation message (stderr)

newspapers.cpp: In function 'void dfs1(int, int)':
newspapers.cpp:87:7: warning: unused variable 'ci' [-Wunused-variable]
   87 |   int ci = 0;
      |       ^~
newspapers.cpp: In function 'void setIO(std::string)':
newspapers.cpp:70:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   70 |     freopen("input.txt", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
newspapers.cpp:71:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   71 |     freopen("output.txt", "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~

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