Submission #786020

#	Time	Username	Problem	Language	Result	Execution time	Memory
786020		gagik_2007	Newspapers (CEOI21_newspapers)	C++17	100 / 100	63 ms	15692 KiB

newspapers

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

#define ff first
#define ss second

ll ttt;
const ll INF=1e18;
const ll MOD=1e9+7;
const ll N=300007;
ll n,m,k;
vector<ll>g[N];
ll sz[N];
bool used[N];
ll head[N];

void dfs(int v, int par=-1){
    // cout<<"YOO"<<endl;
    sz[v]=0;
    for(int to:g[v]){
        if(to!=par){
            dfs(to,v);
            sz[v]=max(sz[v],sz[to]+1);
        }
    }
}

bool is_tree(int c, int v, int par=-1){
    used[v]=true;
    head[v]=c;
    bool retval=true;
    for(int to:g[v]){
        if(to!=par){
            if(used[to])retval= false;
            else if(!is_tree(c,to,v))retval= false;
        }
    }
    return retval;
}

void construct(vector<int>& p, int v, int par=-1){
    // cout<<"CONSTRUCT: "<<v<<" "<<par<<endl;
    dfs(v);
    // cout<<"SZ: ";
    // for(int vv=1;vv<=n;vv++)cout<<sz[vv]<<" ";
    // cout<<endl;
    p.push_back(v);
    int u=-1;
    for(int to:g[v]){
        if(to!=par){
            if(sz[to]==1){
                p.push_back(to);
                p.push_back(v);
            }
            else if(sz[to]!=0) u=to;
        }
    }
    if(u!=-1)construct(p,u,v);
}

int find_leaf(int v, int par=-1){
    dfs(v);
    for(int to:g[v]){
        if(to!=par){
            if(sz[to]>=2){
                return find_leaf(to,v);
            }
        }
    }
    for(int to:g[v]){
        if(sz[to]==1)return to;
    }
    return v;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    // freopen("output.txt","w",stdout);
    // freopen("input.txt","r",stdin);
    cin>>n>>m;
    // if(m!=n-1)cout<<"NO\n";
    for(int i=0;i<m;i++){
        int x,y;
        cin>>x>>y;
        g[x].push_back(y);
        g[y].push_back(x);
    }
    if(n==1&&m==0){
        cout<<"YES 1 1\n";
        return 0;
    }
    for(int v=1;v<=n;v++){
        if(!used[v]&&!is_tree(v,v)){
            cout<<"NO\n";
            return 0;
        }
    }
    for(int v=1;v<=n;v++){
        dfs(v);
        int cnt=0;
        for(int to:g[v]){
            cnt+=(sz[to]>=2);
        }
        if(cnt>2){
            cout<<"NO\n";
            return 0;
        }
    }
    cout<<"YES\n";
    vector<int>p;
    int leaf=find_leaf(1);
    // cout<<"leaf: "<<leaf<<endl;
    construct(p,leaf);
    if(p.size()>=3&&p[p.size()-1]==p[p.size()-3])p.pop_back();
    int len=p.size();
    for(int i=len-1;i>=0;i--){
        p.push_back(p[i]);
    }
    cout<<p.size()<<endl;
    for(int x:p)cout<<x<<" ";
    cout<<endl;
}

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