graph/Course Schedule at master · jt112/graph · GitHub

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
//g++  5.4.0

#include<bits/stdc++.h>
using namespace std;

#define int long long
#define pb push_back
#define pii pair<int,int>
#define ff first
#define ss second
#define fast ios::sync_with_stdio(0) , cin.tie(0) , cout.tie(0) ;

const int nax= 1e5+10;
vector<int> adj[nax];
vector<int> visit(nax,0);
int n,m;
stack<int> s;

void topologicalsort(int i)
{
    visit[i] = 1;
    for(int j=0;j<adj[i].size();j++)
    {
        if(!visit[adj[i][j]])
            topologicalsort(adj[i][j]);
        else if( visit[adj[i][j]] == 1 )
        {
            cout << "IMPOSSIBLE";
            exit(0);
        }
    }
    visit[i] = 2;
    s.push(i);
}
int main()
{
    fast;
    cin>>n>>m;
    for(int i=0;i<m;i++)
    {
        int u,v;
        cin>>u>>v;
        adj[u].push_back(v);
    }
    for(int i=1;i<=n;i++)
    {
        if(!visit[i])
            topologicalsort(i);
    }
    while(!s.empty())
    {
        cout<<s.top()<<" ";
        s.pop();
    }
}