Submission #618744

#	Time	Username	Problem	Language	Result	Execution time	Memory
618744		drdilyor	Newspapers (CEOI21_newspapers)	C++17	100 / 100	64 ms	4572 KiB

newspapers

#include <bits/stdc++.h>
#ifdef ONPC
    #include "t_debug.cpp"
#else
    #define debug(...) 42
#endif
#define sz(a) ((int)(a).size())
using namespace std;
using ll = long long;
const int INF = 1e9;
const ll INFL = 1e18;
const int RANDOM = chrono::high_resolution_clock::now().time_since_epoch().count();
mt19937 rng(RANDOM);
template<typename T, typename U> istream& operator>>(istream& is, pair<T, U>& p) { return is >> p.first >> p.second; }
const int N = 2e5, LOGN = 17, MOD = 1e9+7;

int solve() {
    int n;
    if (!(cin >> n)) {
        return 1;
    }
    int m; cin >> m;
    vector<vector<int>> adj(n);
    for (int i = 0;i < m; i++) {
        int u, v;
        cin >> u >> v;
        u--; v--;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

    if (m != n-1) {cout << "NO\n"; return 0;}

    if (n == 1) {cout << "YES\n1\n1\n"; return 0;}
    if (n == 2) {cout << "YES\n2\n1 1\n"; return 0;}
    bool yes = true;

    function<pair<int,int>(int,int)> depth = [&](int i, int p)->pair<int,int> {
        int res = 0, rese = i;
        for (int e : adj[i]) {
            if (e != p) {
                auto [d, v] = depth(e, i);
                if (d+1 > res) {
                    res = d+1;
                    rese = v;
                }
            }
        }
        return {res, rese};
    };

    auto [_d, d1] = depth(0, -1);
    auto [_dd, d2] = depth(d1, -1);

    vector<int> path = {d1};
    vector<int> visited(n);
    function<bool(int)> findD = [&](int i) {
        if (visited[i]) return false;
        if (i == d2) return true;
        visited[i] = true;
        for (int e : adj[i]) {
            path.push_back(e);
            if (findD(e)) return true;
            path.pop_back();
        }
        return false;
    };
    findD(d1);
    debug(d1, d2, path);
    vector<int> res;

    for (int i = 1; i < sz(path)-1; i++) {
        int v = path[i];
        int dep = 0;
        res.push_back(v);
        for (int e : adj[v]) {
            if (e == path[i-1] || e == path[i+1]) continue;
            auto [de, end] = depth(e, v); de++;
            if (de > 2) yes = false;
            if (de > 1) {
                res.push_back(e);
                res.push_back(v);
            }
        }
    }

    cout << (yes ? "YES" : "NO") << '\n';

    if (yes) {
        cout << sz(res) * 2 << '\n';
        for (int i : res) cout << i +1 << ' ';
        for (auto it = res.rbegin(); it != res.rend(); it++) {
            cout<< *it+1 << ' ';
        }
        cout << '\n';
    }

    return 0;
}

signed main() {
    cin.tie(0)->sync_with_stdio(0);
    int t = 1;
    #ifdef ONPC
    t = 10000;
    #endif
    while (t-- && cin) {
        if (solve()) break;
        #ifdef ONPC
            cout << "____________________" << endl;
        #endif
    }
    return 0;
}

/*
     █████               █████  ███  ████                               
    ▒▒███               ▒▒███  ▒▒▒  ▒▒███                               
  ███████  ████████   ███████  ████  ▒███  █████ ████  ██████  ████████ 
 ███▒▒███ ▒▒███▒▒███ ███▒▒███ ▒▒███  ▒███ ▒▒███ ▒███  ███▒▒███▒▒███▒▒███
▒███ ▒███  ▒███ ▒▒▒ ▒███ ▒███  ▒███  ▒███  ▒███ ▒███ ▒███ ▒███ ▒███ ▒▒▒ 
▒███ ▒███  ▒███     ▒███ ▒███  ▒███  ▒███  ▒███ ▒███ ▒███ ▒███ ▒███     
▒▒████████ █████    ▒▒████████ █████ █████ ▒▒███████ ▒▒██████  █████    
 ▒▒▒▒▒▒▒▒ ▒▒▒▒▒      ▒▒▒▒▒▒▒▒ ▒▒▒▒▒ ▒▒▒▒▒   ▒▒▒▒▒███  ▒▒▒▒▒▒  ▒▒▒▒▒     
                                            ███ ▒███                    
                                           ▒▒██████                     
                                            ▒▒▒▒▒▒
*/

Compilation message (stderr)

newspapers.cpp: In function 'int solve()':
newspapers.cpp:5:24: warning: statement has no effect [-Wunused-value]
    5 |     #define debug(...) 42
      |                        ^~
newspapers.cpp:69:5: note: in expansion of macro 'debug'
   69 |     debug(d1, d2, path);
      |     ^~~~~
newspapers.cpp:74:13: warning: unused variable 'dep' [-Wunused-variable]
   74 |         int dep = 0;
      |             ^~~

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