CodeForces 687A NP-Hard Problem

 1 #include<iostream>
 2 #include<algorithm>
 3 #include<set>
 4 #include<cstdio>
 5 #include<cstdlib>
 6 #include<cmath>
 7 #include<vector>
 8 using namespace std;
 9 #define FOR(i,j,k) for(int i=j;i<=k;i++)
10 #define FORD(i,j,k) for(int i=j;i>=k;i--)
11 #define LL long long
12 #define maxn 100010
13 #define SZ(x) int(x.size())
14 int n,m,j,x,y;
15 bool flag=true;
16 vector<int> a[maxn];
17 vector<int> ans[2];
18 int col[maxn],len[maxn],vis[maxn];
19 bool dfs(int s,int color)
20 {
21     col[s]=color;
22     vis[s]=1;
23     FOR(i,0,SZ(a[s])-1)
24     {
25     if(vis[a[s][i]]) {if(col[a[s][i]]==color) return false;}
26     else if(!dfs(a[s][i],-color)) return false;
27     }
28     if(color==1) ans[0].push_back(s); else ans[1].push_back(s);
29     return true;
30 }
31 int main()
32 {
33 cin>>n>>m;
34 FOR(i,1,m)
35 {
36     cin>>x>>y;
37     a[x].push_back(y);
38     a[y].push_back(x);
39 }
40 FOR(i,1,n)
41 {
42 if(!vis[i]) if(!dfs(i,1)) flag=false;
43 }
44 if(flag) 
45 FOR(i,0,1)
46 {
47     cout<<SZ(ans[i])<<endl;
48     FOR(j,0,SZ(ans[i])-1) cout<<ans[i][j]<<‘ ‘;
49     cout<<endl;
50 }
51 else cout<<-1<<endl;
52 return 0;
53 }