#include <bits/stdc++.h>
//#pragma GCC target("sse,sse2")
//#pragma GCC optimize("unroll-loops,O3")
#define rep(i,l,r) for (int i = l; i < r; i++)
#define repr(i,r,l) for (int i = r; i >= l; i--)
#define X first
#define Y second
#define all(x) (x).begin() , (x).end()
#define pb push_back
#define endl '\n'
#define debug(x) cerr << #x << " : " << x << endl;
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int,int> pll;
constexpr int N = 1e5+5,mod = 1e9+7,inf = 1e9+10;
inline int mkay(int a,int b){
if (a+b >= mod) return a+b-mod;
if (a+b < 0) return a+b+mod;
return a+b;
}
inline int poww(int a,int k){
if (k < 0) return 0;
int z = 1;
while (k){
if (k&1) z = 1ll*z*a%mod;
a = 1ll*a*a%mod;
k >>= 1;
}
return z;
}
int n,m,h[N],lw[N],dp[N][2][2][2]; // root bega
bool vis[N];
int mark[N];
vector<int> adj[N];
void pre(int v,int p){
lw[v] = inf;
vis[v] = 1;
for (int u : adj[v]){
if (u == p) continue;
if (vis[u] && h[u] < h[v]){
mark[v] = v;
lw[v] = h[u];
continue;
}
if (vis[u]) continue;
h[u] = h[v]+1;
pre(u,v);
if (lw[u] <= h[v]){
mark[v] = u;
lw[v] = lw[u];
}
}
}
void dfs(int v){
vis[v] = 1;
for (int u : adj[v]) if (!vis[u])
dfs(u);
if (lw[v] > n){
dp[v][1][0][0] = 1;
dp[v][0][0][0] = 1;
dp[v][1][0][1] = 1;
int t = 0;
for (int u : adj[v]){
if (h[u] == h[v]+1){
t++;
dp[v][0][0][0] = mkay(dp[v][0][0][0],mkay(dp[u][0][0][0],dp[u][0][0][1]));
dp[v][1][0][0] = 1ll*dp[v][1][0][0]*mkay(dp[u][1][0][0],dp[u][1][0][1])%mod;
}
}
dp[v][0][0][0] = mkay(dp[v][0][0][0],dp[v][1][0][0]-t);
dp[v][1][0][0] = mkay(dp[v][1][0][0],1);
return;
}
if (mark[v] == v){
int t = 0;
dp[v][0][0][1] = 1;
dp[v][1][1][0] = 1;
dp[v][1][1][1] = 1;
dp[v][1][0][1] = 1;
for(int u : adj[v]){
if (h[u] == h[v]+1){
t++;
dp[v][0][0][1] = mkay(dp[v][0][0][1],mkay(dp[u][0][0][0],dp[u][0][0][1]));
dp[v][1][1][0] = 1ll*dp[v][1][1][0]*mkay(dp[u][1][0][0],dp[u][1][0][1])%mod;
}
}
dp[v][0][1][0] = dp[v][1][1][0];
dp[v][0][0][1] = mkay(dp[v][0][0][1],-t);
dp[v][0][1][1] = dp[v][0][0][1];
return;
}
if(lw[v] < h[v]){
int t = 0;
dp[v][1][0][1] = 1;
dp[v][1][1][1] = 1;
dp[v][1][0][0] = 1;
dp[v][1][1][0] = 1;
for (int u : adj[v]){
if (h[u] == h[v]+1){
t++;
if (u == mark[v]){
dp[v][0][0][1] = mkay(dp[v][0][0][1],dp[u][0][1][1]);
dp[v][1][0][1] = 1ll*dp[v][1][0][1]*dp[u][1][0][1]%mod;
dp[v][0][1][1] = mkay(dp[v][0][1][1],dp[u][0][1][1]);
dp[v][1][1][1] = 1ll*dp[v][1][1][1]*dp[u][1][1][1]%mod;
dp[v][0][0][0] = mkay(dp[v][0][0][0],dp[u][0][1][0]);
dp[v][0][1][0] = mkay(dp[v][0][1][0],dp[u][0][1][0]);
dp[v][1][1][0] = 1ll*dp[v][1][1][0]*dp[u][1][1][0]%mod;
dp[v][1][0][0] = 1ll*dp[v][1][0][0]*dp[u][0][0][0]%mod;
}
else{
dp[v][0][0][1] = mkay(dp[v][0][0][1],mkay(dp[u][0][0][0],dp[u][0][0][1]));
dp[v][1][0][1] = 1ll*dp[v][1][0][1]*mkay(dp[u][1][0][1],dp[u][1][0][0])%mod;
dp[v][0][1][1] = mkay(dp[v][0][1][1],mkay(dp[u][0][0][1],dp[u][0][0][0]));
dp[v][1][1][1] = 1ll*dp[v][1][1][1]*mkay(dp[u][1][1][0],dp[u][1][1][1])%mod;
dp[v][1][1][0] = 1ll*dp[v][1][1][0]*mkay(dp[u][1][0][1],dp[u][1][0][0])%mod;
dp[v][1][0][0] = 1ll*dp[v][1][0][0]*mkay(dp[u][1][0][0],dp[u][1][0][1])%mod;
}
}
}
dp[v][0][0][1] = mkay(dp[v][0][0][1],-(t-1)+dp[v][1][0][1]);
dp[v][0][1][1] = mkay(dp[v][0][1][1],-(t-1)+dp[v][1][1][1]);
dp[v][0][0][0] = mkay(dp[v][0][0][0],dp[v][1][0][0]);
dp[v][0][1][0] = mkay(dp[v][0][1][0],dp[v][1][1][0]);
dp[v][1][1][1] = mkay(dp[v][1][1][1],1);
dp[v][1][0][1] = mkay(1,dp[v][1][0][1]);
return;
}
dp[v][1][0][0] = 1;
dp[v][1][0][1] = 1;
int t = 0;
for (int u : adj[v]){
if (h[u] == h[v]+1){
t++;
if (u == mark[v]){
dp[v][1][0][0] = 1ll*dp[v][1][0][0]*dp[u][0][0][0]%mod;
dp[v][1][0][1] = 1ll*dp[v][1][0][1]*dp[u][1][0][1]%mod;
dp[v][0][0][1] = mkay(dp[v][0][0][1],mkay(dp[u][0][1][1],dp[u][0][1][0]));
}
else{
dp[v][1][0][0] = 1ll*dp[v][1][0][0]*mkay(dp[u][1][0][1],dp[u][1][0][0])%mod;
dp[v][1][0][1] = 1ll*dp[v][1][0][1]*mkay(dp[u][1][0][1],dp[u][1][0][0])%mod;
dp[v][0][0][1] = mkay(dp[v][0][0][1],mkay(dp[u][0][0][1],dp[u][0][0][0]));
}
}
}
dp[v][1][0][1] = mkay(dp[v][1][0][1],1);
dp[v][0][0][1] = mkay(dp[v][0][0][1],dp[v][1][0][1]-t);
dp[v][0][0][0] = dp[v][1][0][0];
}
int main(){
ios :: sync_with_stdio(0); cin.tie(0);
cin >> n >> m;
rep(i,0,m){
int u,v;
cin >> u >> v;
adj[u].pb(v);
adj[v].pb(u);
}
pre(1,0);
memset(vis,0,sizeof vis);
dfs(1);
dp[1][0][0][0] = mkay(dp[1][0][0][0],dp[1][0][0][1]-1);
cout << dp[1][0][0][0];
return 0;
}
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
1 ms |
2772 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
2 ms |
2772 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
1 ms |
2772 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
1 ms |
2772 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
