#include <bits/stdc++.h>
using namespace std;
#define st first
#define nd second
#define pb push_back
#define sz(x) (int)(x).size()
#define ll long long
ll mod=1000000007;
int inf=1000000007;
ll infl=1000000000000000007;
vector<pair<int,int>>G[200007];
int low[200007];
bool odw[200007];
int nr[200007];
int ban,ban1;
ll ans,br;
ll n,m,a,b,c;
void dfs(int v,int k)
{
odw[v]=1;
nr[v]=c++;
low[v]=nr[v];
for(auto u:G[v])
{
if(u.nd==ban||u.nd==ban1) continue;
if(!odw[u.st])
{
dfs(u.st,u.nd);
low[v]=min(low[v],low[u.st]);
}
else if(u.nd!=k&&nr[u.st]<nr[v]) low[v]=min(low[v],nr[u.st]);
}
if(k>ban&&low[v]==nr[v]) br++;
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin>>n>>m;
for(int i=1;i<=m;i++)
{
cin>>a>>b;
G[a].pb({b,i});
G[b].pb({a,i});
}
for(ll i=1;i<=m;i++)
{
for(ll j=i+1;j<=m;j++)
{
ban1=i;
ban=j;
br=0;
c=1;
for(int l=1;l<=n;l++) odw[l]=0;
dfs(1,-1);
int x=1;
for(int l=1; l<=n; l++) x&=odw[l];
if(!x) ans+=m-j;
else ans+=br;
}
}
cout<<ans<<endl;
return 0;
}
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 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 | #include <bits/stdc++.h> using namespace std; #define st first #define nd second #define pb push_back #define sz(x) (int)(x).size() #define ll long long ll mod=1000000007; int inf=1000000007; ll infl=1000000000000000007; vector<pair<int,int>>G[200007]; int low[200007]; bool odw[200007]; int nr[200007]; int ban,ban1; ll ans,br; ll n,m,a,b,c; void dfs(int v,int k) { odw[v]=1; nr[v]=c++; low[v]=nr[v]; for(auto u:G[v]) { if(u.nd==ban||u.nd==ban1) continue; if(!odw[u.st]) { dfs(u.st,u.nd); low[v]=min(low[v],low[u.st]); } else if(u.nd!=k&&nr[u.st]<nr[v]) low[v]=min(low[v],nr[u.st]); } if(k>ban&&low[v]==nr[v]) br++; } int main() { ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0); cin>>n>>m; for(int i=1;i<=m;i++) { cin>>a>>b; G[a].pb({b,i}); G[b].pb({a,i}); } for(ll i=1;i<=m;i++) { for(ll j=i+1;j<=m;j++) { ban1=i; ban=j; br=0; c=1; for(int l=1;l<=n;l++) odw[l]=0; dfs(1,-1); int x=1; for(int l=1; l<=n; l++) x&=odw[l]; if(!x) ans+=m-j; else ans+=br; } } cout<<ans<<endl; return 0; } |
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