Submission #576736

#	Time	Username	Problem	Language	Result	Execution time	Memory
576736		talant117408	Newspapers (CEOI21_newspapers)	C++17	52 / 100	65 ms	4544 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], color(N);
int depth[N], furthest[N];
vector <int> diameter, order;
int df, vf, in_diameter[N];

void find_furthest(int v, int p, int dist) {
    order.pb(v);
    if (dist > df) {
        df = dist;
        vf = v;
        diameter = order;
    }
    for (auto to : graph[v]) {
        if (to == p) continue;
        find_furthest(to, v, dist+1);
    }
    order.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 dfs3(int v, int p, int c) {
    color[v] = c;
    for (auto to : graph[v]) {
        if (to == p) continue;
        dfs3(to, v, 1-c);
    }
}

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;
    }
    
    
    dfs3(1, 1, 1);
    int forbidden, start = 1, forbidden_leaves = 0;
    for (int i = 1; i <= n; i++) {
        if (sz(graph[i]) == 1) {
            start = graph[i][0];
            forbidden = color[i];
            break;
        }
    }
    for (int i = 1; i <= n; i++) {
        if (sz(graph[i]) == 1 && forbidden == color[i]) {
            forbidden_leaves++;
        }
    }
    set <int> visited;
    vector <int> orderr;
    int add = 1;
    function <void(int, int)> dfs2 = [&](int v, int p) {
        if (add) {                                     
            visited.insert(v);
            orderr.pb(v);
        }
        if (sz(visited) == n-forbidden_leaves) {
            add = 0;
        }
        for (auto to : graph[v]) {
            if (to == p) continue;
            if (sz(graph[to]) == 1 && color[to] == forbidden) continue;
            dfs2(to, v);
            if (add) {
                visited.insert(v);
                orderr.pb(v);
            }
        }
    };
    dfs2(start, start);
    cout << "YES" << endl;
    cout << sz(orderr)*2 << endl;
    for (auto to : orderr) cout << to << ' ';
    for (auto to : orderr) 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: 6 / 8
• Subtask 3: 40 / 80