#include <bits/stdc++.h>
using namespace std;
mt19937 rng(time(NULL));
typedef pair<int,int> pii;
int n,m;
vector<pii> edges;
vector<int> muchii[1005];
vector<int> v;
bool adj[1005][1005];
int dp[1005][22],par[1005],dist[1005][1005],niv[1005],in[1005],out[1005],from[1005];
int comp[1005];
int use[1005];
int Dp[1005];
auto S=chrono::steady_clock::now();
int timp;
bool isancestor(int a,int b)
{
return in[a]<=in[b]&&out[a]>=out[b];
}
int LCA(int a,int b)
{
if(niv[a]>niv[b])
swap(a,b);
if(isancestor(a,b))
return a;
for(int i=12;i>=0;i--)
if(dp[a][i]!=0&&!isancestor(dp[a][i],b))
a=dp[a][i];
return par[a];
}
void Dfs(int nod)
{
timp++;
in[nod]=timp;
use[nod]=1;
dp[nod][0]=par[nod];
for(int i=1;i<=12;i++)
dp[nod][i]=dp[dp[nod][i-1]][i-1];
for(int i:muchii[nod])
if(i!=par[nod])
{
par[i]=nod;
niv[i]=niv[nod]+1;
Dfs(i);
}
out[nod]=timp;
}
bool cmp(pii a, pii b)
{
int d1=dist[a.first][a.second];
int d2=dist[b.first][b.second];
return d1<d2;
}
bool block[1005];
int start;
void dfs(int nod)
{
auto E=chrono::steady_clock::now();
int x=chrono::duration_cast<chrono::milliseconds>(E - S).count();
if(v.size()>=21)
return;
if(x>=990)
{
cout<<"no";
exit(0);
}
use[nod]=v.size();
bool good=1;
int pmax=0;
int pmin=1e9;
vector<int> mypoz;
for(int i:muchii[nod])
{
if(use[i])
{
if(i==v[v.size()-2])
continue;
if(i==start)
{
if(v.size()>=4);
else
good=0;
}
else if(i!=v[v.size()-2])
good=0;
pmax=max(pmax,use[i]);
pmin=min(pmin,use[i]);
mypoz.push_back(use[i]);
}
}
sort(mypoz.begin(),mypoz.end());
if(v.size()-pmax+1>=4&&pmax!=0)
{
for(int i=pmax-1;i<v.size();i++)
cout<<v[i]<<' ';
exit(0);
}
if(adj[nod][start]&&pmin+1>=4&&pmin!=1e9)
{
for(int i=0;i<pmin;i++)
cout<<v[i]<<' ';
cout<<nod;
exit(0);
}
for(int i=1;i<mypoz.size();i++)
{
int st=mypoz[i-1];
int dr=mypoz[i];
if(dr-st+2>=4)
{
for(int j=st-1;j<dr;j++)
cout<<v[j]<<' ';
cout<<nod;
exit(0);
}
}
if(good)
{
for(int i:muchii[nod])
if(!use[i])
{
v.push_back(i);
dfs(i);
use[i]=0;
v.pop_back();
}
}
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
cin>>n>>m;
for(int i=1;i<=n;i++)
comp[i]=i;
for(int i=1;i<=m;i++)
{
int a,b;
cin>>a>>b;
if(comp[a]!=comp[b])
{
muchii[a].push_back(b);
muchii[b].push_back(a);
int c2=comp[b];
for(int j=1;j<=n;j++)
if(comp[j]==c2)
comp[j]=comp[a];
}
else
edges.push_back({a,b});
}
for(int i=1;i<=n;i++)
if(!use[i])
{
timp=0;
niv[i]=1;
Dfs(i);
}
for(int i=1;i<=n;i++)
for(int j=1;j<=n;j++)
if(comp[i]==comp[j])
{
int lca=LCA(i,j);
dist[i][j]=niv[i]-niv[lca]+niv[j]-niv[lca]+1;
}
sort(edges.begin(),edges.end(),cmp);
for(auto i:edges)
{
int a=i.first;
int b=i.second;
muchii[a].push_back(b);
muchii[b].push_back(a);
int lca=LCA(a,b);
vector<int> v1,v2;
while(a!=lca)
{
v1.push_back(a);
a=par[a];
}
while(b!=lca)
{
v2.push_back(b);
b=par[b];
}
v.clear();
for(auto j:v1)
v.push_back(j);
v.push_back(lca);
reverse(v2.begin(),v2.end());
for(auto j:v2)
v.push_back(j);
vector<int> vals;
for(int j=0;j<v.size();j++)
{
if(j==0)
Dp[v[j]]=1;
else
Dp[v[j]]=1e9;
int x=v[j];
from[x]=0;
for(int k=j-1;k>=0;k--)
{
int y=v[k];
if(adj[x][y]||k==j-1)
{
Dp[x]=min(Dp[x],Dp[y]+1);
if(Dp[y]+1==Dp[x])
from[x]=y;
}
}
}
int last=v.back();
if(Dp[last]>=4)
{
vector<int> vals;
while(true)
{
vals.push_back(last);
if(last==v[0])
break;
last=from[last];
}
for(int j:vals)
cout<<j<<' ';
return 0;
}
adj[i.first][i.second]=adj[i.second][i.first]=1;
}
v.clear();
vector<int> nodes;
for(int i=1;i<=n;i++)
shuffle(muchii[i].begin(),muchii[i].end(),rng);
for(int i=1;i<=n;i++)
nodes.push_back(i);
shuffle(nodes.begin(),nodes.end(),rng);
for(int i:nodes)
{
start=i;
v.clear();
v.push_back(i);
for(int j=1;j<=n;j++)
use[j]=0;
dfs(i);
}
cout<<"no";
return 0;
}
Compilation message
indcyc.cpp: In function 'void dfs(int)':
indcyc.cpp:95:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
95 | for(int i=pmax-1;i<v.size();i++)
| ~^~~~~~~~~
indcyc.cpp:106:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
106 | for(int i=1;i<mypoz.size();i++)
| ~^~~~~~~~~~~~~
indcyc.cpp: In function 'int main()':
indcyc.cpp:194:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
194 | for(int j=0;j<v.size();j++)
| ~^~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
340 KB |
Output is correct |
| 2 |
Correct |
0 ms |
340 KB |
Output is correct |
| 3 |
Correct |
1 ms |
340 KB |
Output is correct |
| 4 |
Correct |
0 ms |
340 KB |
Output is correct |
| 5 |
Correct |
1 ms |
340 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
340 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
0 ms |
340 KB |
Output is correct |
| 2 |
Correct |
0 ms |
340 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
724 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
6 ms |
852 KB |
Output is correct |
| 2 |
Correct |
591 ms |
852 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
969 ms |
1972 KB |
Output is correct |
| 2 |
Correct |
5 ms |
1876 KB |
Output is correct |
| 3 |
Correct |
6 ms |
1928 KB |
Output is correct |
| 4 |
Correct |
984 ms |
2028 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
27 ms |
1980 KB |
Output is correct |
| 2 |
Correct |
968 ms |
1960 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
52 ms |
6300 KB |
Output is correct |
| 2 |
Correct |
52 ms |
5740 KB |
Output is correct |
| 3 |
Correct |
985 ms |
6284 KB |
Output is correct |
| 4 |
Correct |
982 ms |
5856 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
154 ms |
5804 KB |
Output is correct |
| 2 |
Correct |
977 ms |
5748 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
365 ms |
4296 KB |
Output is correct |
| 2 |
Correct |
961 ms |
4648 KB |
Output is correct |
| 3 |
Correct |
52 ms |
7000 KB |
Output is correct |
| 4 |
Correct |
973 ms |
7032 KB |
Output is correct |
