#include<bits/stdc++.h>
#define int long long
#define pb push_back
#define fi first
#define se second
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int maxN = 6e5 + 5;
const int mod = 1e9 + 7;
const ll oo = 1e18;
int n, m;
pair<int, int> e[maxN];
vector<int> adj[maxN];
pair<int, int> a[maxN];
int lab[maxN];
int c[maxN];
int lg[maxN], f[maxN][21];
int depth[maxN];
int Findset(int u)
{
return lab[u] < 0 ? u : lab[u] = Findset(lab[u]);
}
void Unite(int u, int v)
{
int r = Findset(u), s = Findset(v);
if(r == s)
return;
if(lab[r] > lab[s])
swap(r, s);
lab[r] += lab[s];
lab[s] = r;
}
void Log()
{
for(int i=2; i<maxN; i++)
lg[i] = lg[i / 2] + 1;
}
void predfs(int u, int par)
{
for(int v : adj[u])
{
if(v == par)
continue;
f[v][0] = u;
depth[v] = depth[u] + 1;
for(int i=1; i<=18; i++)
f[v][i] = f[f[v][i - 1]][i - 1];
predfs(v, u);
}
}
int LCA(int u, int v)
{
if(depth[u] < depth[v])
swap(u, v);
int k = depth[u] - depth[v];
for(int i=18; i>=0; i--)
{
if(k & (1 << i))
{
u = f[u][i];
k -= (1 << i);
}
}
if(u == v)
return u;
for(int i=18; i>=0; i--)
{
if(f[u][i] != f[v][i])
{
u = f[u][i];
v = f[v][i];
}
}
return f[u][0];
}
int jump(int x, int k)
{
for(int i=18; i>=0; i--)
if(k & (1 << i))
{
x = f[x][i];
k -= (1 << i);
}
return x;
}
void ReadInput()
{
cin >> n >> m;
for(int i=1; i<n; i++)
{
int u, v;
cin >> u >> v;
e[i] = {u, v};
adj[u].pb(v);
adj[v].pb(u);
}
for(int i=1; i<=m; i++)
cin >> a[i].fi >> a[i].se;
}
int d[maxN];
void dfs(int u, int par)
{
for(int v : adj[u])
{
if(v == par)
continue;
dfs(v, u);
d[u] += d[v];
}
if(d[u] && par)
{
//cout << u << " ";
Unite(u, par);
Unite(u + n, par + n);
}
}
int mark[maxN];
void Solve()
{
predfs(1, 0);
memset(lab, -1, sizeof lab);
// for(int i=1; i<=m; i++) cout << a[i].fi << " " << a[i].se << '\n';return;
//cout << LCA(6, 10);return;
for(int i=1; i<=m; i++)
{
int t = LCA(a[i].fi, a[i].se);
int px = 0, py = 0;
if(t != a[i].fi)
{
px = jump(a[i].fi, depth[a[i].fi] - depth[t] - 1);
d[a[i].fi]++;
d[px]--;
}
if(t != a[i].se)
{
py = jump(a[i].se, depth[a[i].se] - depth[t] - 1);
d[a[i].se]++;
d[py]--;
}
if(px && py)
{
Unite(px, py + n);
Unite(py, px + n);
}
// cout << a[i].fi << " " << a[i].se << '\n';continue;
// cout << t << " " << px << " " << py << '\n';
}
dfs(1, 0);
int res = 1;
for(int i=2; i<=n; i++)
{
if(Findset(i) == Findset(i + n))
{
cout << 0;
return;
}
if(!mark[Findset(i)])
{
mark[Findset(i)] = 1;
res *= 2;
}
if(!mark[Findset(i + n)])
mark[Findset(i + n)] = 1;
res %= mod;
}
cout << res;
}
int32_t main()
{
//freopen("x.inp", "r", stdin);
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
Log();
ReadInput();
Solve();
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
127 ms |
60236 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
262 ms |
126732 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
14 ms |
24044 KB |
Output is correct |
| 2 |
Correct |
13 ms |
24276 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
12 ms |
24148 KB |
Output is correct |
| 2 |
Correct |
14 ms |
24340 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
16 ms |
25216 KB |
Output is correct |
| 2 |
Correct |
14 ms |
25032 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
17 ms |
25164 KB |
Output is correct |
| 2 |
Correct |
17 ms |
25044 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
391 ms |
110844 KB |
Output is correct |
| 2 |
Correct |
369 ms |
110992 KB |
Output is correct |
| 3 |
Correct |
235 ms |
75688 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
442 ms |
110756 KB |
Output is correct |
| 2 |
Correct |
422 ms |
110796 KB |
Output is correct |
| 3 |
Correct |
339 ms |
78572 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
404 ms |
111088 KB |
Output is correct |
| 2 |
Correct |
386 ms |
110988 KB |
Output is correct |
| 3 |
Correct |
267 ms |
78452 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
389 ms |
111400 KB |
Output is correct |
| 2 |
Correct |
370 ms |
111364 KB |
Output is correct |
| 3 |
Correct |
235 ms |
75560 KB |
Output is correct |
