제출 #528513

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
528513		Rafi22	Newspapers (CEOI21_newspapers)	C++14	100 / 100	17 ms	460 KiB

newspapers

#include <bits/stdc++.h>

using namespace std;

#define endl '\n'
#define st first
#define nd second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define ll long long
ll mod=1000000007;
int inf=1000000007;
ll infl=1000000000000000007;

vector<int>G[1007];
int d[1007];
int h[1007];
int o[1007];
bool is[1007];

void dfs(int v)
{
    h[v]=1;
    for(auto u:G[v])
    {
        if(u==o[v]) continue;
        o[u]=v;
        d[u]=d[v]+1;
        dfs(u);
        h[v]=max(h[v],h[u]+1);
    }
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int n,m,a,b;
    cin>>n>>m;
    if(m!=n-1)
    {
        cout<<"NO";
        return 0;
    }
    if(n<=2)
    {
        cout<<"YES"<<endl<<n<<endl<<1<<" ";
        if(n==2) cout<<1;
        return 0;
    }
    for(int i=0;i<n-1;i++)
    {
        cin>>a>>b;
        G[a].pb(b);
        G[b].pb(a);
    }
    for(int i=1;i<=n;i++)
    {
        o[i]=0;
        dfs(i);
        int c=0;
        for(auto u:G[i]) if(h[u]>2) c++;
        if(c>2)
        {
            cout<<"NO";
            return 0;
        }
    }
    cout<<"YES"<<endl;
    o[1]=0;
    d[1]=0;
    dfs(1);
    int mx=0,p1,p2;
    for(int i=1;i<=n;i++)
    {
        if(d[i]>mx)
        {
            mx=d[i];
            p1=i;
        }
    }
    o[p1]=0;
    d[p1]=0;
    dfs(p1);
    mx=0;
    for(int i=1;i<=n;i++)
    {
        if(d[i]>mx)
        {
            mx=d[i];
            p2=i;
        }
    }
    vector<int>diam;
    while(p2!=p1)
    {
        if(d[p2]!=mx) diam.pb(p2);
        is[p2]=1;
        p2=o[p2];
    }
    vector<int>vec,ans;
    for(auto v:diam)
    {
        vec.pb(v);
        for(auto u:G[v])
        {
            if(!is[u]&&sz(G[u])>1)
            {
                vec.pb(u);
                vec.pb(v);
            }
        }
    }
    for(auto x:vec) ans.pb(x);
    reverse(all(vec));
    for(auto x:vec) ans.pb(x);
    cout<<sz(ans)<<endl;
    for(auto x:ans) cout<<x<<" ";


    return 0;
}

컴파일 시 표준 에러 (stderr) 메시지

newspapers.cpp: In function 'int main()':
newspapers.cpp:97:13: warning: 'p1' may be used uninitialized in this function [-Wmaybe-uninitialized]
   97 |     while(p2!=p1)
      |           ~~^~~~

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