This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#pragma GCC optimize("O3","unroll-loops")
#include <bits/stdc++.h>
#define pb push_back
using namespace std;
typedef long long ll;
vector<ll> G[100005];
ll low[100005],dfn[100005],avsub[100005],sub[100005],dft;
ll ans,c;
stack<ll> st;
bitset<100005> vis;
void con(int u)
{
vis[u]=1,++c;
for(ll i:G[u])
if(!vis[i])
con(i);
}
void dfs(int u,int f)
{
ll usq=0;
low[u]=dfn[u]=++dft,sub[u]=1,ans+=(c-1)*(c-1),avsub[u]=1;
st.push(u);
for(ll i:G[u])
if(i!=f)
if(!dfn[i])
{
dfs(i,u),sub[u]+=sub[i];
if(low[i]>=dfn[u])
{
ll sq=0;
vector<ll> v;
avsub[u]+=sub[i];
for(int x=-1;x!=i;)
x=st.top(),st.pop(),sq+=avsub[x]*avsub[x],v.pb(x);
for(ll j:v)
ans-=(c-sub[i])*(c-sub[i])+sq;
}
else
low[u]=min(low[u],low[i]);
}
else if(dfn[u]>dfn[i])
low[u]=min(low[u],dfn[i]);
}
int main()
{
ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
ll m,a,b,n;
cin >> n >> m;
while(m--)
cin >> a >> b,G[a].pb(b),G[b].pb(a);
for(int i=1;i<=n;++i)
if(!vis[i])
c=0,con(i),dfs(i,i);
cout << ans << "\n";
}
Compilation message (stderr)
count_triplets.cpp: In function 'void dfs(int, int)':
count_triplets.cpp:38:13: warning: unused variable 'j' [-Wunused-variable]
for(ll j:v)
^
count_triplets.cpp:27:5: warning: suggest explicit braces to avoid ambiguous 'else' [-Wdangling-else]
if(i!=f)
^
count_triplets.cpp:23:5: warning: unused variable 'usq' [-Wunused-variable]
ll usq=0;
^~~
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