#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define rng(i,c,n) for(int i=c;i<n;i++)
#define fi first
#define se second
#define pb push_back
#define sz(a) (int)a.size()
#define vec(...) vector<__VA_ARGS__>
#define _3xaMC2q ios::sync_with_stdio(0),cin.tie(0)
typedef long long ll;
using pii=pair<int,int>;
using vi=vector<int>;
void print(){cout<<'\n';}
template<class h,class...t>
void print(const h&v,const t&...u){cout<<v<<' ',print(u...);}
//e
#define vp vec(pii)
const int _n=300001,lon=21;
int n,m;
vi adj[_n];
map<pii,int> es;
int spr[lon][_n*3+11],prs[lon][_n];
int par[_n],dpth[_n],tin[_n];
int _tm;
vi tour;
void dfs(int v){
tin[v]=_tm++;
tour.pb(v);
for(auto u:adj[v]){
if(u==par[v]) continue;
dpth[u]=dpth[v]+1;
par[u]=v;
dfs(u);
tour.pb(v);
_tm++;
}
}
int chmin(int v,int u){
return dpth[v]<dpth[u]?v:u;
}
void _gap_lca(){
dfs(0);
rep(i,n){
prs[0][i]=par[i];
}
rng(j,1,lon){
rep(i,n){
int up=prs[j-1][i];
prs[j][i]=up==-1?up:prs[j-1][up];
}
}
const int si_to=sz(tour);
rep(i,si_to){
spr[0][i]=tour[i];
if(i+1<si_to){
spr[0][i]=chmin(spr[0][i],tour[i+1]);
}
}
rng(j,1,lon){
rep(i,si_to){
int up=spr[j-1][i];
if(i+(1<<(j-1))<si_to){
up=chmin(up,spr[j-1][i+(1<<(j-1))]);
}
spr[j][i]=up;
}
}
}
int get_ancestor(int u,int v){
int i=tin[u],j=tin[v];
if(i==j) return v;
if(i>j)swap(i,j),swap(u,v);
int k=31-__builtin_clz(j-i);
u=spr[k][i];
v=spr[k][j-(1<<k)];
return chmin(u,v);
}
int get_dist(int u,int v){
int up=get_ancestor(u,v);
return dpth[v]+dpth[u]-2*dpth[up];
}
int push_up(int s,int d){
per(i,lon){
if(d>>i&1){
s=prs[i][s];
}
}
return s;
}
signed main(){
_3xaMC2q;
cin>>n>>m;
rep(i,n-1){
int u,v;
cin>>u>>v;
u-=1,v-=1;
es[minmax(u,v)]=i;
adj[u].pb(v);
adj[v].pb(u);
}
_gap_lca();
vi rbe(n,-1);
//denotes edge from (i,pari)
vec(vp) g(n-1);
//denotes graph of edges in inital graph
rep(i,m){
int s,t;
cin>>s>>t;
s-=1,t-=1;
if(dpth[s]>dpth[t])swap(s,t);
if(s!=t){
int up=get_ancestor(s,t);
if(up!=s){
int ds=get_dist(s,up);
int ns=push_up(s,ds-1);
int id=s;
rbe[id]=rbe[id]==-1?ns:chmin(rbe[id],ns);
int dt=get_dist(t,up);
int nt=push_up(t,dt-1);
id=t;
rbe[id]=rbe[id]==-1?nt:chmin(rbe[id],nt);
int u=es[minmax(ns,up)],v=es[minmax(nt,up)];
g[u].pb(pii(1,v));
g[v].pb(pii(1,u));
}else{
int dt=get_dist(t,up);
int nt=push_up(t,dt-1);
int id=t;
rbe[id]=rbe[id]==-1?nt:chmin(rbe[id],nt);
}
}
}
//add additional edges from rbe
vi rbts;
rep(i,n)rbts.pb(i);
sort(rbts.begin(),rbts.end(),[&](int l,int r){return dpth[l]>dpth[r];});
for(auto s:rbts){
if(rbe[s]!=-1){
if(dpth[rbe[s]]<dpth[s]){
int up=rbe[s];
rbe[par[s]]=rbe[par[s]]==-1?up:chmin(rbe[par[s]],up);
int u=es[minmax(s,par[s])],v=es[minmax(par[s],par[par[s]])];
g[u].pb(pii(0,v));
g[v].pb(pii(0,u));
}
}
}
bool valid=1;
vi usd(n-1,-1);
auto rfs=[&](auto self,int v)->void{
for(auto e:g[v]){
int u=e.se;
int w=e.fi;
if(usd[u]==-1){
usd[u]=usd[v]^w;
self(self,u);
}else if(usd[u]!=(usd[v]^w)){
valid=0;
}
}
};
ll ans=1;
const ll mod=1000000007;
rep(i,n-1){
if(usd[i]==-1){
usd[i]=0;
ans=ans*2%mod;
ans%=mod;
rfs(rfs,i);
}
}
if(!valid){
print(0);
}else{
print(ans);
}
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
127 ms |
54512 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
292 ms |
146896 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
4 ms |
8020 KB |
Output is correct |
| 2 |
Correct |
6 ms |
8452 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
5 ms |
8100 KB |
Output is correct |
| 2 |
Correct |
5 ms |
8512 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
9 ms |
9684 KB |
Output is correct |
| 2 |
Correct |
9 ms |
9684 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
11 ms |
9812 KB |
Output is correct |
| 2 |
Correct |
10 ms |
9696 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
522 ms |
130048 KB |
Output is correct |
| 2 |
Correct |
535 ms |
131120 KB |
Output is correct |
| 3 |
Correct |
356 ms |
90168 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
603 ms |
134328 KB |
Output is correct |
| 2 |
Correct |
562 ms |
133036 KB |
Output is correct |
| 3 |
Correct |
370 ms |
92980 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
584 ms |
133348 KB |
Output is correct |
| 2 |
Correct |
518 ms |
130068 KB |
Output is correct |
| 3 |
Correct |
374 ms |
91960 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
547 ms |
134880 KB |
Output is correct |
| 2 |
Correct |
532 ms |
133428 KB |
Output is correct |
| 3 |
Correct |
466 ms |
90968 KB |
Output is correct |
