#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll MOD = 1e9 + 7;
vector<int> par;
vector<vector<int>> g;
void dfs(int v, int p){
par[v] = p;
for (int u: g[v]){
if (u == p) continue;
dfs(u, v);
}
}
struct dsu{
int c;
vector<int> p;
dsu(int n): p(n, -1), c(n) {}
int find(int v){
if (p[v] < 0) return v;
return p[v] = find(p[v]);
}
void merge(int a, int b){
a = find(a), b = find(b);
if (a == b) return;
if (-p[a] < -p[b]) swap(a, b);
p[a] += p[b];
p[b] = a;
c--;
}
int get_co() {return c;}
void merge_set(vector<int> &a){
for (int i=1; i<a.size(); i++) merge(a[0], a[i]);
}
};
ll binpow(ll a, ll b){
ll r = 1;
for (; b; b >>= 1, a = a*a % MOD)
if (b & 1) r = r*a % MOD;
return r;
}
signed main(){
cin.tie(0)->sync_with_stdio(0);
int n, m, k; cin >> n >> m >> k;
g.resize(n), par.resize(n);
for (int i=1; i<n; i++){
int a, b; cin >> a >> b;
a--, b--;
g[a].push_back(b);
g[b].push_back(a);
}
dfs(0, -1);
vector<vector<int>> sets(m);
for (int i=0; i<m; i++){
int a, b; cin >> a >> b;
a--, b--;
vector<int> l;
while (a != -1){
l.push_back(a);
a = par[a];
}
vector<int> r;
while (b != -1){
r.push_back(b);
b = par[b];
}
while (l.size() && r.size() && l.back() == r.back()) l.pop_back(), r.pop_back();
sets[i].insert(sets[i].end(), l.begin(), l.end());
sets[i].insert(sets[i].end(), r.rbegin(), r.rend());
}
ll result = 0;
for (int i=(1<<m)-1; i>=0; i--){
dsu ds(n);
for (int j=0; j<m; j++){
if (i & (1<<j)){
ds.merge_set(sets[j]);
}
if (__builtin_parityll(i)){
result -= binpow(k, ds.get_co()-1);
}
else{
result += binpow(k, ds.get_co()-1);
}
}
}
cout << (result % MOD + MOD) % MOD << "\n";
}
Compilation message
Main.cpp: In constructor 'dsu::dsu(int)':
Main.cpp:16:17: warning: 'dsu::p' will be initialized after [-Wreorder]
16 | vector<int> p;
| ^
Main.cpp:15:9: warning: 'int dsu::c' [-Wreorder]
15 | int c;
| ^
Main.cpp:17:5: warning: when initialized here [-Wreorder]
17 | dsu(int n): p(n, -1), c(n) {}
| ^~~
Main.cpp: In member function 'void dsu::merge_set(std::vector<int>&)':
Main.cpp:32:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
32 | for (int i=1; i<a.size(); i++) merge(a[0], a[i]);
| ~^~~~~~~~~
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
0 ms |
212 KB |
Output is correct |
2 |
Correct |
0 ms |
212 KB |
Output is correct |
3 |
Correct |
0 ms |
212 KB |
Output is correct |
4 |
Correct |
0 ms |
212 KB |
Output is correct |
5 |
Correct |
0 ms |
212 KB |
Output is correct |
6 |
Correct |
0 ms |
212 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
0 ms |
212 KB |
Output is correct |
2 |
Correct |
1 ms |
212 KB |
Output is correct |
3 |
Correct |
1 ms |
212 KB |
Output is correct |
4 |
Correct |
1 ms |
212 KB |
Output is correct |
5 |
Correct |
0 ms |
212 KB |
Output is correct |
6 |
Correct |
1 ms |
280 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
0 ms |
212 KB |
Output is correct |
2 |
Correct |
0 ms |
212 KB |
Output is correct |
3 |
Correct |
0 ms |
212 KB |
Output is correct |
4 |
Correct |
1 ms |
212 KB |
Output is correct |
5 |
Correct |
2 ms |
212 KB |
Output is correct |
6 |
Correct |
0 ms |
212 KB |
Output is correct |
7 |
Correct |
1 ms |
212 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
0 ms |
212 KB |
Output is correct |
2 |
Correct |
0 ms |
212 KB |
Output is correct |
3 |
Correct |
0 ms |
212 KB |
Output is correct |
4 |
Correct |
0 ms |
212 KB |
Output is correct |
5 |
Correct |
3 ms |
212 KB |
Output is correct |
6 |
Correct |
3 ms |
212 KB |
Output is correct |
7 |
Correct |
0 ms |
212 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
0 ms |
212 KB |
Output is correct |
2 |
Correct |
0 ms |
212 KB |
Output is correct |
3 |
Correct |
0 ms |
212 KB |
Output is correct |
4 |
Correct |
0 ms |
212 KB |
Output is correct |
5 |
Correct |
0 ms |
212 KB |
Output is correct |
6 |
Correct |
0 ms |
212 KB |
Output is correct |
7 |
Correct |
0 ms |
212 KB |
Output is correct |
8 |
Correct |
1 ms |
212 KB |
Output is correct |
9 |
Correct |
1 ms |
212 KB |
Output is correct |
10 |
Correct |
1 ms |
212 KB |
Output is correct |
11 |
Correct |
0 ms |
212 KB |
Output is correct |
12 |
Correct |
1 ms |
280 KB |
Output is correct |
13 |
Correct |
0 ms |
212 KB |
Output is correct |
14 |
Correct |
0 ms |
212 KB |
Output is correct |
15 |
Correct |
0 ms |
212 KB |
Output is correct |
16 |
Correct |
1 ms |
212 KB |
Output is correct |
17 |
Correct |
2 ms |
212 KB |
Output is correct |
18 |
Correct |
0 ms |
212 KB |
Output is correct |
19 |
Correct |
1 ms |
212 KB |
Output is correct |
20 |
Correct |
0 ms |
212 KB |
Output is correct |
21 |
Correct |
0 ms |
212 KB |
Output is correct |
22 |
Correct |
0 ms |
212 KB |
Output is correct |
23 |
Correct |
0 ms |
212 KB |
Output is correct |
24 |
Correct |
3 ms |
212 KB |
Output is correct |
25 |
Correct |
3 ms |
212 KB |
Output is correct |
26 |
Correct |
0 ms |
212 KB |
Output is correct |
27 |
Correct |
11 ms |
212 KB |
Output is correct |
28 |
Correct |
0 ms |
212 KB |
Output is correct |
29 |
Correct |
0 ms |
212 KB |
Output is correct |
30 |
Correct |
14 ms |
212 KB |
Output is correct |
31 |
Correct |
4 ms |
324 KB |
Output is correct |
32 |
Correct |
2 ms |
212 KB |
Output is correct |
33 |
Correct |
1 ms |
212 KB |
Output is correct |
34 |
Correct |
1 ms |
212 KB |
Output is correct |
35 |
Correct |
6 ms |
212 KB |
Output is correct |
36 |
Correct |
25 ms |
212 KB |
Output is correct |
37 |
Correct |
12 ms |
324 KB |
Output is correct |