#pragma GCC optimize("Ofast")
#pragma GCC optimization ("O3")
#pragma GCC optimization ("unroll-loops")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
#define mp make_pair
#define eb emplace_back
#define pb push_back
#define e1 first
#define e2 second
#define uint unsigned int
#define ll long long
#define ull unsigned long long
#define ld long double
#define float long double
#define size(x) (int)x.size()
#define satori int testCases; cin>>testCases; while(testCases--)
#define fastio ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0)
#define all(r) begin(r),end(r)
#define time chrono::high_resolution_clock().now().time_since_epoch().count()
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> ordered_set;
mt19937 rng(chrono::high_resolution_clock().now().time_since_epoch().count());
///////////////////
#define debug if(false)
///////////////////
const int MAXN=2e5+10;
vector<pair<int,int>> g[MAXN];
int low[MAXN],dep[MAXN];
bitset<MAXN> bridge,begbridge,vis;
int a,b;
void comp_low(int u,int pe,int d=0){
vis[u]=true;
low[u]=d;
dep[u]=d;
for(auto v:g[u]){
if(v.e2==pe||v.e2==a||v.e2==b)
continue;
if(!vis[v.e1]){
comp_low(v.e1,v.e2,d+1);
low[u]=min(low[u],low[v.e1]);
}
else{
low[u]=min(low[u],dep[v.e1]);
}
}
if(pe&&low[u]==d)
bridge[pe]=true;
}
int solve(int i,int j,int n,int m){
a=i,b=j;
if(begbridge[a]||begbridge[b])
return m-2;
for(int i=1;i<=n;i++)
vis[i]=false;
for(int i=1;i<=m;i++)
bridge[i]=false;
comp_low(1,0);
for(int i=1;i<=n;i++)
if(!vis[i])
return m-2;
int result=0;
for(int i=1;i<=m;i++)
if(i!=a&&i!=b&&bridge[i])
result++;
return result;
}
int32_t main()
{
fastio;
int n,m,u,v;
cin>>n>>m;
for(int i=1;i<=m;i++){
cin>>u>>v;
g[u].eb(mp(v,i));
g[v].eb(mp(u,i));
}
comp_low(1,0);
for(int i=1;i<=m;i++)
begbridge[i]=bridge[i];
ll res=0;
for(int i=1;i<=m;i++)
for(int j=1;j<i;j++){
debug{
if(i==2&&j==1){
cout<<i<<' '<<j<<' '<<solve(i,j,n,m)<<'\n';
for(int i=1;i<=m;i++)
cout<<bridge[i]<<' ';
cout<<'\n';
}}
res+=solve(i,j,n,m);
}
res/=3ll;
cout<<res<<'\n';
}
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 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 | #pragma GCC optimize("Ofast") #pragma GCC optimization ("O3") #pragma GCC optimization ("unroll-loops") #include <bits/stdc++.h> #include <ext/pb_ds/assoc_container.hpp> #include <ext/pb_ds/tree_policy.hpp> using namespace __gnu_pbds; using namespace std; #define mp make_pair #define eb emplace_back #define pb push_back #define e1 first #define e2 second #define uint unsigned int #define ll long long #define ull unsigned long long #define ld long double #define float long double #define size(x) (int)x.size() #define satori int testCases; cin>>testCases; while(testCases--) #define fastio ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0) #define all(r) begin(r),end(r) #define time chrono::high_resolution_clock().now().time_since_epoch().count() typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> ordered_set; mt19937 rng(chrono::high_resolution_clock().now().time_since_epoch().count()); /////////////////// #define debug if(false) /////////////////// const int MAXN=2e5+10; vector<pair<int,int>> g[MAXN]; int low[MAXN],dep[MAXN]; bitset<MAXN> bridge,begbridge,vis; int a,b; void comp_low(int u,int pe,int d=0){ vis[u]=true; low[u]=d; dep[u]=d; for(auto v:g[u]){ if(v.e2==pe||v.e2==a||v.e2==b) continue; if(!vis[v.e1]){ comp_low(v.e1,v.e2,d+1); low[u]=min(low[u],low[v.e1]); } else{ low[u]=min(low[u],dep[v.e1]); } } if(pe&&low[u]==d) bridge[pe]=true; } int solve(int i,int j,int n,int m){ a=i,b=j; if(begbridge[a]||begbridge[b]) return m-2; for(int i=1;i<=n;i++) vis[i]=false; for(int i=1;i<=m;i++) bridge[i]=false; comp_low(1,0); for(int i=1;i<=n;i++) if(!vis[i]) return m-2; int result=0; for(int i=1;i<=m;i++) if(i!=a&&i!=b&&bridge[i]) result++; return result; } int32_t main() { fastio; int n,m,u,v; cin>>n>>m; for(int i=1;i<=m;i++){ cin>>u>>v; g[u].eb(mp(v,i)); g[v].eb(mp(u,i)); } comp_low(1,0); for(int i=1;i<=m;i++) begbridge[i]=bridge[i]; ll res=0; for(int i=1;i<=m;i++) for(int j=1;j<i;j++){ debug{ if(i==2&&j==1){ cout<<i<<' '<<j<<' '<<solve(i,j,n,m)<<'\n'; for(int i=1;i<=m;i++) cout<<bridge[i]<<' '; cout<<'\n'; }} res+=solve(i,j,n,m); } res/=3ll; cout<<res<<'\n'; } |
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