Korn

input/code.cpp: In function 'void solve()':
input/code.cpp:89:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                     if (v[i].size() == p->first) ans.push_back(i);
                                           ^
input/code.cpp:99:64: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             for (int i = 1; i <= n; i++) if (v[i].size() == p->first) ei = i;
                                                                ^
input/code.cpp:104:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                     if (v[i].size() == t && !e[i]) {
                                        ^
input/code.cpp: In function 'bool bdfs(int, int, int)':
input/code.cpp:133:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int j = 0; j < v[i].size(); j++) {
                                   ^

#include <bits/stdc++.h>

#define uint unsigned int
#define ull unsigned long long
#define INF 999999999
#define LINF 999999999999999999
#define ll long long
#define ld long double
#define M 1000000007
#define E 0.0000001
#define N (1<<18)
#define pii pair<int, int>
#define pll pair<long long, long long>
#define pdd pair<double, double>
#define pld pair<long double, long double>
#define cll complex<long long>
#define cld complex<long double>
#define X real()
#define Y imag()
#define C 'a'
#define F first
#define S second
#define PI 3.1415926535897932384626433

using namespace std;

vector<pair<int, int>> v[500001];
bool e[500001];
int ei;

//#define cin in
//ifstream in;

void gen () {
    srand(time(0));
    ofstream out("google.in");
    set<pair<int, int>> s;
    int n = 15;
    int w = n - 1 + (rand() % n);
    int m = 1;
    for (int i = 0; i < w; i++) {
        int a = rand() % min(n, m);
        int b = rand() % min(n, m + 1);
        a++;
        b++;
        if (b == m + 1) m++;
        if (a > b) swap(a, b);
        if (a - b) s.insert({a, b});
    }
    out<<m<<" "<<s.size()<<endl;
    for (auto a : s) {
        out<<a.first<<" "<<a.second<<endl;
    }
    out.close();
}

bool dfs (int i, bool f) {
    if (i == ei) return 1;
    if (e[i]) return 1;
    e[i] = true;
    if (v[i].size() > 2 && !f) return 0;
    for (auto j : v[i]) if (!dfs(j.first, false)) return false;
    return true;
}

void solve () {
    int n, m;
    cin>>n>>m;
    for (int i = 0; i < m; i++) {
        int a, b;
        cin>>a>>b;
        v[a].push_back({b, i});
        v[b].push_back({a, i});
    }
    map<int, int> w;
    for (int i = 1; i <= n; i++) {
        if (v[i].size() % 2) {
            cout<<0<<endl;
            return;
        }
        w[v[i].size()]++;
    }
    if (w.size() > 1) {
        auto p = --(w.end());
        if (w.size() == 2) {
            if (p->second < 3) {
                vector<int> ans;
                for (int i = 1; i <= n; i++) {
                    if (v[i].size() == p->first) ans.push_back(i);
                }
                cout<<ans.size()<<endl;
                for (int i : ans) cout<<i<<" ";
                cout<<endl;
            } else {
                cout<<0<<endl;
            }
        } else if (p->second > 1) cout<<0<<endl;
        else {
            for (int i = 1; i <= n; i++) if (v[i].size() == p->first) ei = i;
            --p;
            while (true) {
                int t = p->first;
                for (int i = 1; i <= n; i++) {
                    if (v[i].size() == t && !e[i]) {
                        if (!dfs(i, true)) {
                            cout<<0<<endl;
                            return;
                        }
                    }
                }
                if (p == w.begin()) break;
                --p;
            }
            cout<<1<<endl<<ei<<endl;
        }
    } else if (w.size() == 1) {
        if (w.begin()->first == 2) {
            cout<<n<<endl;
            for (int i = 1; i <= n; i++) cout<<i<<" ";
            cout<<endl;
        } else cout<<0<<endl;
    }
}

int x[100000];
int it = 1;

bool bdfs (int i, int l, int be) {
    if (l == 0 && i == be) {
        return true;
    }
    bool any = false;
    for (int j = 0; j < v[i].size(); j++) {
        auto a = *(v[i].begin() + j);
        if (x[a.second] == it) continue;
        x[a.second] = it;
        v[i].erase(v[i].begin() + j);
        bool b = bdfs(a.first, l - 1, be);
        any = any || b;
        v[i].insert(v[i].begin() + j, a);
        x[a.second] = it - 1;
        if (!b) return false;
    }

    return any;
}

void brute () {
    int n, m;
    cin>>n>>m;
    for (int i = 0; i < m; i++) {
        int a, b;
        cin>>a>>b;
        v[a].push_back({b, i});
        v[b].push_back({a, i});
    }
    vector<int> ans;
    for (int i = 1; i <= n; i++) {
        if (bdfs(i, m, i)) ans.push_back(i);
        it++;
    }
    cout<<ans.size()<<endl;
    for (int i : ans) cout<<i<<" ";
    cout<<endl;
}

int main () {
    //while (true) {
        /*gen();
        cout<<"BRUTE "<<endl;
        for (int i = 0; i < 500001; i++) e[i] = false, v[i].clear();
        in.open("google.in");
        brute();
        in.close();
        in.open("google.in");
        cout<<"SOLVE "<<endl;
        for (int i = 0; i < 500001; i++) e[i] = false, v[i].clear();
        */solve();
        //in.close();
        //char c;
        //scanf("%c", &c);
    //}
}

/**
9 12
1 2
1 3
1 4
1 5
1 6
1 7
2 8
3 8
4 9
5 9
6 9
7 9
*/

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: WRONG ANSWER

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: WRONG ANSWER

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: WRONG ANSWER

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: WRONG ANSWER

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: WRONG ANSWER

Test 20

Verdict: ACCEPTED

Test 21

Verdict: ACCEPTED

Test 22

Verdict: WRONG ANSWER

Test 23

Verdict: ACCEPTED

Test 24

Verdict: ACCEPTED

Test 25

Verdict: ACCEPTED

Test 26

Verdict: ACCEPTED

Test 27

Verdict: ACCEPTED

Test 28

Verdict: ACCEPTED

Test 29

Verdict: ACCEPTED

Test 30

Verdict: ACCEPTED

Test 31

Verdict: ACCEPTED

Test 32

Verdict: ACCEPTED

Test 33

Verdict: ACCEPTED

Test 34

Verdict: ACCEPTED

Test 35

Verdict: ACCEPTED

Test 36

Verdict: ACCEPTED

Test 37

Verdict: ACCEPTED

Test 38

Verdict: ACCEPTED

Test 39

Verdict: ACCEPTED

Test 40

Verdict: ACCEPTED