Submission #1693310

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll, ll> P;

#define fi first
#define se second
#define repl(i,a,b) for(ll i=(ll)(a);i<(ll)(b);i++)
#define rep(i,n) repl(i,0,n)
#define each(itr,v) for(auto itr:v)
#define pb push_back
#define all(x) (x).begin(),(x).end()
#define dbg(x) cout<<#x"="<<x<<endl
#define mmax(x,y) (x>y?x:y)
#define mmin(x,y) (x<y?x:y)
#define maxch(x,y) x=mmax(x,y)
#define minch(x,y) x=mmin(x,y)
#define uni(x) x.erase(unique(all(x)),x.end())
#define exist(x,y) (find(all(x),y)!=x.end())
#define bcnt __builtin_popcount

#define INF 1e18
#define mod 1000000007

struct UnionFind{
  vector<int> v;
  UnionFind(int n) : v(n, -1) {}
  void init(){ for(int i = 0;i < v.size();i++)v[i]=-1; }
  int find(int x) { return v[x] < 0 ? x : v[x] = find(v[x]); }
  bool unite(int x, int y) {
    x = find(x); y = find(y);
    if (x == y) return false;
    if (-v[x] < -v[y]) swap(x, y);
    v[x] += v[y]; v[y] = x;
    return true;
  }
  bool root(int x) { return v[x] < 0; }
  bool same(int x, int y) { return find(x) == find(y); }
  int size(int x) { return -v[find(x)]; }
};

ll mod_pow(ll a,ll n){
  ll res=1;
  while(n>0){
    if(n&1)res=res*a%mod;
    a=a*a%mod;
    n>>=1;
  }
  return res;
}

ll n,m;
P es[500050];
ll deg[400040];
vector<P> g[400040];
ll cost[500050];

P dfs(ll v,ll pre){
  ll res=0;
  ll cnt=deg[v];
  for(P e : g[v]){
    if(e.fi==pre)continue;
    P tmp=dfs(e.fi,v);
    cnt+=tmp.se;
    res+=tmp.fi;
    if(tmp.se)res=(res+e.se)%mod;
  }
  cnt%=2;
  return P(res,cnt);
}

int main(){
  rep(i,500050){
    cost[i]=mod_pow(2,i+1);
  }
	cin>>n>>m;
  rep(i,m){
    cin>>es[i].fi>>es[i].se;
    es[i].fi--; es[i].se--;
    deg[es[i].fi]++;
    deg[es[i].se]++;
  }
  UnionFind uf(n);
  rep(i,m){
    if(uf.same(es[i].fi,es[i].se))continue;
    uf.unite(es[i].fi,es[i].se);
    g[es[i].fi].push_back(P(es[i].se,cost[i]));
    g[es[i].se].push_back(P(es[i].fi,cost[i]));
  }
  rep(i,n)deg[i]%=2;
  ll res=0;
  rep(i,m)res=(res+cost[i])%mod;
  cout<<(res+dfs(0,-1).fi)%mod<<endl;
	return 0;
}

Submission Info

Judge Result