#include <bits/stdc++.h>
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
//#pragma GCC optimize("unroll-loops")
//#pragma GCC optimize("-O3")
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("fast-math")
//#pragma GCC optimize("no-stack-protector")
#define F first
#define S second
#define sz(x) int(x.size())
#define pb push_back
#define N 300001
#define M ll(1e9 + 7)
#define inf 1e9 + 1e9
using namespace std;
//using namespace __gnu_pbds;
typedef long double ld;
typedef long long ll;
typedef short int si;
typedef array <int, 2> a2;
//typedef tree <int, null_type, less_equal<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
vector <array <int, 2> > g[N], gr[N], qr, v[N];
void add(int a, int b, int c)
{
v[a].pb({b, c});
v[b].pb({a, c});
}
bool mkr[N];
int pr[N], rk[N], t[N + N][20], in[N], tin[N], id, h[N], logs[N + N], mnr[N], nh[N], mt[N];
int fnd(int x) {if (pr[x] != x) pr[x] = fnd(pr[x]); return pr[x];}
set <pair <int, int> > se;
void link(int x, int y)
{
if (rk[x] < rk[y]) swap(x, y);
pr[y] = x;
rk[x] += rk[y];
}
vector <int> vr, to[N], glub[N], lnk[N], a[N];
ll ans = 1;
array <int, 2> pred[N];
void spusk(int v, int p)
{
if (p != -1) h[v] = h[p] + 1; else pred[v] = {-1, -1};
nh[v] = h[v];
glub[h[v]].pb(v);
in[v] = sz(vr);
tin[v] = id++;
vr.pb(v);
for (auto it : g[v])
{
if (it[0] == p) continue;
spusk(it[0], v);
pred[it[0]] = {v, it[1]};
vr.pb(v);
gr[v].pb({tin[it[0]], it[1]});
}
gr[v].pb({int(1e9), int(1e9)});
}
int lca(int a, int b)
{
if (in[a] > in[b]) swap(a, b);
int j = logs[in[b] - in[a] + 1];
a = t[in[a]][j];
b = t[in[b] - (1 << j) + 1][j];
if (h[a] > h[b]) return b;
return a;
}
void dfser(int nd, int p)
{
for (auto it : g[nd])
{
if (it[0] == p) continue;
dfser(it[0], nd);
nh[nd] = min(nh[nd], nh[it[0]]);
if (nh[it[0]] < h[nd]) add(it[0], nd, 0);
}
}
bool check(int nd, int c)
{
if (mt[nd] != -1) return (mt[nd] == c);
mt[nd] = c;
for (auto it : v[nd])
{
if (!check(it[0], (it[1] ^ c))) return 0;
}
return 1;
}
int main()
{
//freopen("input.txt", "r", stdin); //freopen("output4.txt", "w", stdout);
ios_base::sync_with_stdio(0); istream::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int n, m;
cin >> n >> m;
for (int i = 2; i < N + N; i++) logs[i] = 1 + logs[i >> 1];
bool f = 1;
for (int i = 0; i < n - 1; i++)
{
int x, y;
cin >> x >> y;
g[x].pb({y, i});
g[y].pb({x, i});
pr[i] = i;
rk[i] = 1;
}
for (int i = 1; i <= n; i++) if (sz(g[i]) > 2) f = 0;
if (f)
{
int beg;
for (int i = 1; i <= n; i++) if (sz(g[i]) == 1) beg = i;
for (; m > 0 ; m--)
{
int x, y;
cin >> x >> y;
a[x].pb(m);
a[y].pb(m);
}
vector <int> vr; vr.clear();
int v = beg, p = -1;
while (v != -1)
{
int nxt = -1;
vr.pb(v);
for (auto it : g[v])
{
if (it[0] == p) continue;
nxt = it[0];
}
p = v;
v = nxt;
}
ll ans = 1;
set <int> se; se.clear();
for (int i = 0; i < sz(vr); i++)
{
bool f = 1;
if (i != 0 && sz(se) == 0) {f = 0; ans = (ans + ans) % M;}
for (auto it : a[vr[i]])
{
if (se.find(it) == se.end()) se.insert(it);
else se.erase(it);
}
if (i != 0 && f && sz(se) == 0) ans = (ans + ans) % M;
}
cout << ans << endl;
exit(0);
}
spusk(1, -1);
for (int i = 0; i < sz(vr); i++) t[i][0] = vr[i];
for (int j = 1; j < 20; j++)
for (int i = 0; i < sz(vr); i++)
{
int a = t[i][j - 1];
int b = t[min(sz(vr) - 1, i + (1 << (j - 1)))][j - 1];
if (h[a] > h[b]) t[i][j] = b; else t[i][j] = a;
}
for (int i = 1; i <= n; i++) mnr[i] = -1;
for (int i = 0; i < m; i++)
{
int x, y;
cin >> x >> y;
qr.pb({x, y});
se.insert({x, y});
se.insert({y, x});
int lc = lca(x, y);
nh[x] = min(nh[x], h[lc]);
nh[y] = min(nh[y], h[lc]);
if (lc != x && lc != y) add(x, y, 1);
if (lc == x) to[y].pb(x);
else if (lc == y) to[x].pb(y);
else
{
to[x].pb(lc);
to[y].pb(lc);
int pos1 = upper_bound(gr[lc].begin(), gr[lc].end(), a2{tin[x], int(1e9)}) - gr[lc].begin() - 1;
int pos2 = upper_bound(gr[lc].begin(), gr[lc].end(), a2{tin[y], int(1e9)}) - gr[lc].begin() - 1;
int x = fnd(gr[lc][pos1][1]), y = fnd(gr[lc][pos2][1]);
if (x != y) link(x, y);
}
}
dfser(1, 1);
memset(mt, -1, sizeof(mt));
for (int i = 2; i <= n; i++)
{
if (mt[i] != -1) continue;
if (!check(i, 0)) {cout << 0 << endl; exit(0);}
}
memset(mkr, 0, sizeof(mkr));
for (int i = N - 1; i >= 0; i--)
for (auto v : glub[i])
{
int root = -1;
if (sz(lnk[v]) != 0)
{
root = lnk[v][0];
for (auto it : lnk[v])
{
int x = fnd(root), y = fnd(it);
if (x != y) link(x, y);
}
}
int mn = -1;
for (auto it : to[v])
if (mn == -1 || h[mn] > h[it]) mn = it;
if (mnr[v] != -1 && (mn == -1 || h[mn] > h[mnr[v]])) mn = mnr[v];
if (mn == v || mn == -1) continue;
int nxt = pred[v][0], nm = pred[v][1];
if (nxt == -1) continue;
if (mn != nxt) lnk[nxt].pb(nm);
if (mnr[nxt] == -1 || h[mnr[nxt]] > h[mn]) mnr[nxt] = mn;
if (mnr[v] != -1 && mnr[v] != v)
{
int x = fnd(root), y = fnd(nm);
if (x != y) link(x, y);
}
}
for (int i = 0; i < n - 1; i++)
{
int id = fnd(i);
if (mkr[id]) continue;
mkr[id] = 1;
ans = (ans + ans) % M;
}
cout << ans << endl;
}
Compilation message
usmjeri.cpp: In function 'int main()':
usmjeri.cpp:184:17: warning: 'beg' may be used uninitialized in this function [-Wmaybe-uninitialized]
int v = beg, p = -1;
^
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
289 ms |
65264 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
490 ms |
76900 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
46 ms |
54016 KB |
Output is correct |
| 2 |
Correct |
40 ms |
53988 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
41 ms |
54016 KB |
Output is correct |
| 2 |
Correct |
42 ms |
54008 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
58 ms |
55800 KB |
Output is correct |
| 2 |
Correct |
48 ms |
54776 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
53 ms |
55680 KB |
Output is correct |
| 2 |
Correct |
43 ms |
54784 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1260 ms |
174060 KB |
Output is correct |
| 2 |
Correct |
1325 ms |
177628 KB |
Output is correct |
| 3 |
Correct |
712 ms |
124604 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1629 ms |
179292 KB |
Output is correct |
| 2 |
Correct |
1576 ms |
178932 KB |
Output is correct |
| 3 |
Correct |
975 ms |
138212 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1298 ms |
179856 KB |
Output is correct |
| 2 |
Correct |
1219 ms |
176092 KB |
Output is correct |
| 3 |
Correct |
960 ms |
138728 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1204 ms |
180572 KB |
Output is correct |
| 2 |
Correct |
1148 ms |
180784 KB |
Output is correct |
| 3 |
Correct |
624 ms |
125156 KB |
Output is correct |
