Submission #576766

#	Time	Username	Problem	Language	Result	Execution time	Memory
576766		talant117408	Newspapers (CEOI21_newspapers)	C++17	54 / 100	76 ms	5064 KiB

newspapers

#include <bits/stdc++.h>
 
using namespace std;
 
typedef long long ll;
typedef pair <int, int> pii;
typedef pair <ll, ll> pll;

#define long                unsigned long 
#define pb                  push_back
#define mp                  make_pair
#define all(v)              (v).begin(),(v).end()
#define rall(v)             (v).rbegin(),(v).rend()
#define lb                  lower_bound
#define ub                  upper_bound
#define sz(v)               int((v).size())
#define do_not_disturb      ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define endl                '\n'

const int N = 1e3+3;
vector <int> graph[N];
int depth[N], furthest[N];
vector <int> diameter, tmp;
int df, vf, in_diameter[N];

void find_furthest(int v, int p, int dist) {
    tmp.pb(v);
    if (dist > df) {
        df = dist;
        vf = v;
        diameter = tmp;
    }
    for (auto to : graph[v]) {
        if (to == p) continue;
        find_furthest(to, v, dist+1);
    }
    tmp.pop_back();
}

int dfs(int v, int p) {
    int mx = depth[v];
    for (auto to : graph[v]) {
        if (to == p || in_diameter[to]) continue;
        depth[to] = depth[v] + 1;
        mx = max(mx, dfs(to, v));
    }
    furthest[v] = mx;
    return mx;
}

void solve() {
    int n, m;
    cin >> n >> m;
    for (int i = 1; i <= m; i++) {
        int a, b;
        cin >> a >> b;
        graph[a].pb(b);
        graph[b].pb(a);
    }
    
    if (m >= n) {
        cout << "NO" << endl;
        return;
    }
    
    find_furthest(1, 1, 0);
    df = 0;
    find_furthest(vf, vf, 0);
    df = 0;
    for (auto to : diameter) in_diameter[to] = 1;
    for (int i = 0; i < sz(diameter); i++) {
        auto to = diameter[i];
        dfs(to, to);
        if (furthest[to] >= 3 && i >= 3 && i <= n-4) {
            df++;
        }
    }
    if (df) {
        cout << "NO" << endl;
        return;
    }
    
    vector <int> order;
    for (int i = 1; i < sz(diameter)-1; i++) {
        order.pb(diameter[i]);
        for (auto to : graph[diameter[i]]) {
            if (to == diameter[i+1] || to == diameter[i-1] || sz(graph[to]) == 1) continue;
            order.pb(to); order.pb(to);
            order.pb(diameter[i]);
        }
    }
    reverse(all(diameter));
    for (int i = 1; i < sz(diameter)-1; i++) {
        order.pb(diameter[i]);
        for (auto to : graph[diameter[i]]) {
            if (to == diameter[i+1] || to == diameter[i-1] || sz(graph[to]) == 1) continue;
            order.pb(to); order.pb(to);
            order.pb(diameter[i]);
        }
    }
    
    cout << "YES" << endl;
    if (n == 1) {
        cout << "1\n1";
        return;
    }
    else if (n == 2) {
        cout << "2\n1 1";
        return;
    }
    cout << sz(order) << endl;
    for (auto to : order) cout << to << ' ';
}

int main() {
    do_not_disturb
    
    int t = 1;
    //~ cin >> t;
    while (t--) {
        solve();
    }
    
    return 0;
}
/*
12 11
1 2
2 3
3 4
4 5
5 6
6 7
7 8
4 9
9 10
10 11
5 12
*/

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