Submission #530895

#	Time	Username	Problem	Language	Result	Execution time	Memory
530895		azberjibiou	Newspapers (CEOI21_newspapers)	C++17	100 / 100	68 ms	6356 KiB

newspapers

#include <bits/stdc++.h>
#define gibon ios::sync_with_stdio(false); cin.tie(0);
#define fir first
#define sec second
#define pii pair<int, int>
#define pll pair<ll, ll>
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
typedef long long ll;
using namespace std;
int dx[4]={0, 1, 0, -1}, dy[4]={1, 0, -1 , 0};
const int mxN=1005;
const int mxM=1010;
const int mxK=105;
const int MOD=1000000007;
const ll INF=1e15;
const ll P1=1000000007;
const ll P2=1000000009;
int N, M;
vector <int> v[mxN], child[mxN];
int dis[mxN];
void dfs0(int now, int pre)
{
    for(int nxt : v[now])   if(nxt!=pre)
    {
        dis[nxt]=dis[now]+1;
        dfs0(nxt, now);
    }
}
int sub[mxN];
bool ok=true;
void dfs1(int now, int pre)
{
    int cnt2=0;
    for(int nxt : v[now])   if(nxt!=pre)
    {
        dis[nxt]=dis[now]+1;
        child[now].push_back(nxt);
        dfs1(nxt, now);
        sub[now]=max(sub[nxt]+1, sub[now]);
        if(sub[nxt]>=2) cnt2++;
    }
    if(cnt2>=2) ok=false;
}
vector <int> ans;
int ncnt;
bool dfs2(int now)
{
    ncnt--;
    ans.push_back(now);
    if(ncnt==0) return false;
    sort(child[now].begin(), child[now].end(), [](int a, int b){return sub[a]<sub[b];});
    for(int nxt : child[now])
    {
        if(sub[nxt]==1)
        {
            if(!dfs2(nxt))  return false;
            ans.push_back(now);
        }
        if(sub[nxt]>=2) if(dfs2(nxt))   return false;
    }
    return true;
}
int main()
{
    gibon
    cin >> N >> M;
    for(int i=0;i<M;i++)
    {
        int a, b;   cin >> a >> b;
        v[a].push_back(b);
        v[b].push_back(a);
    }
    if(M>=N)
    {
        cout << "NO";
        return 0;
    }
    if(N==1)
    {
        cout << "YES\n1\n1";
        return 0;
    }
    if(N==2)
    {
        cout << "YES\n2\n1 1";
        return 0;
    }
    dfs0(1, -1);
    int far=1;
    for(int i=2;i<=N;i++)   if(dis[far]<dis[i]) far=i;
    for(int i=1;i<=N;i++)   dis[i]=0;
    dfs1(far, -1);
    if(!ok)
    {
        cout << "NO";
        return 0;
    }
    for(int i=1;i<=N;i++)   if(v[i].size()>=2)  ncnt++;
    dfs2(child[far][0]);
    cout << "YES\n";
    cout << 2*ans.size() << '\n';
    for(int i=0;i<ans.size();i++)   cout << ans[i] << " ";
    for(int i=ans.size()-1;i>=0;i--)    cout << ans[i] << " ";
}

Compilation message (stderr)

newspapers.cpp: In function 'int main()':
newspapers.cpp:104:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  104 |     for(int i=0;i<ans.size();i++)   cout << ans[i] << " ";
      |                 ~^~~~~~~~~~~

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