1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

const int       maxn = 500000;

int             n,m;
vector<int>     g[maxn];
int             color[maxn];
vector<int>     cutVertices;
bool            backEdge;
int             degIn[maxn];
int             degOut[maxn];

void dfs(int v)
{
    color[v]=1;
    for(int i=0;i<g[v].size();i++)
        if(!color[g[v][i]])
            dfs(g[v][i]);
        else
            if(color[g[v][i]]==1)
                backEdge=1;
    color[v]=2;
}

int main()
{
    int a,b;
    cin >> n >> m;
    for(int i=0;i<m;i++)
    {
        cin >> a >> b;
        g[--a].push_back(--b);
        degIn[b]++;
        degOut[a]++;
    }
    for(int i=0;i<n;i++)
        if(!color[i])
            dfs(i);
    if(!backEdge)
    {
        cout << "NIE\n";
        return 0;
    }
    for(int i=0;i<n;i++)
    {
        if(degIn[i]>0 && degOut[i]>0)
        {
            backEdge=false;
            for(int j=0;j<n;j++)
                if(j!=i)
                    color[j]=0;
                else
                    color[j]=2;
            for(int j=0;j<n;j++)
                if(!color[j])
                    dfs(j);
            if(!backEdge)
                cutVertices.push_back(i+1);
        }
    }
    cout << cutVertices.size() << '\n';
    if(cutVertices.size()>0)
    {
        for(int i=0;i<cutVertices.size();i++)
            cout << cutVertices[i] << ' ';
        cout << '\n';
    }
    return 0;
}