#include <bits/stdc++.h>
#define int long long
using namespace std;
const int mod = 1e9 + 7;
const int maxn = 1e5 + 10;
int n,m;
vector <int> adj[maxn];
stack <int> st;
int l[maxn],t[maxn],cnt,scc,id[maxn];
int dp[maxn],dp2[maxn],s[maxn];
vector <int> adj2[maxn];
int ans = 0LL;
void dfs(int x, int p)
{
st.push(x);
l[x] = t[x] = ++cnt;
for (int i:adj[x])
if (i!=p)
{
if (!t[i])
{
dfs(i,x);
l[x]=min(l[x],l[i]);
}
else l[x]=min(l[x],t[i]);
}
if (l[x]==t[x])
{
scc++; int temp;
do
{
temp = st.top(); st.pop();
s[scc]++;
id[temp] = scc;
}
while (temp!=x);
}
}
void dfs2(int x, int p)
{
dp[x] = 0;
for (int i:adj2[x])
if (i!=p)
{
dfs2(i,x);
dp[x] = (dp[x] + dp[i] + s[i]) ;
}
}
void dfs3(int x, int p, int val)
{
dp2[x] = val;
vector <int> pre,suf;
for (int i:adj2[x])
if (i!=p)
{
pre.push_back((dp[i]+s[i]) );
suf.push_back((dp[i]+s[i]) );
}
val = (val + s[x]) ;
for (int i=1; i<pre.size(); i++) pre[i] = (pre[i-1] + pre[i]) ;
for (int i=suf.size()-2; i>=0; i--) suf[i] = (suf[i+1] + suf[i]) ;
int cnt=0;
for (int i:adj2[x])
if (i!=p)
{
int val2 = val;
if (cnt>0) val2 = (val2 + pre[cnt-1]) ;
if (cnt+1<suf.size()) val2 = (val2 + suf[cnt+1]) ;
cnt++;
dfs3(i,x,val2);
}
}
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr); cout.tie(nullptr);
cin>>n>>m;
for (int i=1; i<=m; i++)
{
int u,v; cin>>u>>v;
adj[u].push_back(v);
adj[v].push_back(u);
}
cnt = scc= 0;
vector <int> root;
for (int i=1; i<=n; i++) if (!t[i]) dfs(i,i), root.push_back(id[i]);
for (int i=1; i<=n; i++)
for (int j:adj[i])
if (id[i]!=id[j])
{
adj2[id[i]].push_back(id[j]);
}
for (int i:root) dfs2(i,i);
for (int i:root) dfs3(i,i,0);
for (int i=1; i<=scc; i++)
{
int sl = s[i];
int temp = 0;
if (sl>=3)
{
temp = sl*(sl-1)*(sl-2);
ans = (ans + temp);
}
if (sl>=2)
{
temp = (sl-1)*(sl-2) + sl-1;
// cerr<<temp<<endl;
ans = (ans + temp*dp[i]*2);
ans = (ans + temp*dp2[i]*2);
}
ans = (ans + s[i]*dp[i]*dp2[i]*2);
}
int res = 0;
for (int i:root)
{
int p = dp[i] + s[i];
for (int j=1; j<=p; j++) res += 2LL*(j-1)*(p-j);
}
cout<<res<<'\n';
// cout<<ans<<'\n';
// int res=0LL;
// for (int i=2; i<n; i++)
// res+=2*(i-1)*(n-i);
// cout<<res<<'\n';
}
Compilation message
new_home.cpp: In function 'void dfs3(long long int, long long int, long long int)':
new_home.cpp:63:20: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
63 | for (int i=1; i<pre.size(); i++) pre[i] = (pre[i-1] + pre[i]) ;
| ~^~~~~~~~~~~
new_home.cpp:71:22: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
71 | if (cnt+1<suf.size()) val2 = (val2 + suf[cnt+1]) ;
| ~~~~~^~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
3 ms |
4948 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
3 ms |
4948 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
7 ms |
10024 KB |
Execution killed with signal 11 |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
8 ms |
10060 KB |
Execution killed with signal 11 |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
3 ms |
4948 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
3 ms |
4948 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
