#include<bits/stdc++.h>
using namespace std;
using ll = long long;
constexpr int inf = 1e9;
constexpr ll infl = 1e18;
constexpr ll mod = 1e9 + 7;
ll power(ll a, ll b) {
ll res = 1;
while (b-->0) res = res * a % mod;
return res;
}
int main() {
cin.tie(0)->sync_with_stdio(0);
int n, m, k;
cin >> n >> m >> k;
vector<vector<pair<int,int>>> adj(n);
for( int i = 0; i < n-1; i++) {
int a, b;
cin >> a >> b;
a--;b--;
adj[a].emplace_back(b, i);
adj[b].emplace_back(a, i);
}
vector<pair<int,int>> p(m);
for (auto& [i, j] : p) cin >> i >> j, i--,j--;
auto path = [&](auto& path, int i, int j, int p=-1)->optional<vector<int>>{
if (i == j) return vector<int>{};
for (auto [e, ei] : adj[i]) {
if (e == p) continue;
optional<vector<int>> res = path(path, e, j, i);
if (res.has_value()) {
res.value().push_back(ei);
return res;
}
}
return nullopt;
};
auto sub4 = [&]() {
int res = 0;
for (int mask = 0; mask < (1<<(n-1)); mask++) {
bool ok = 1;
for (auto[i, j] : p) {
vector edges = path(path, i, j).value();
int black = 0, white = 0;
for (int e : edges) {
if (mask & (1<<e)) black++;
else white++;
}
if (!black || !white) ok = 0;
if (!ok) break;
}
res += ok;
}
cout << res << endl;
};
auto sub1 = [&]() {
int len = path(path, p[0].first, p[0].second)->size();
cout << (power(k, n-1) - k * power(k, n-1-len) % mod + mod) % mod << endl;
};
auto sub2 = [&]() {
auto p1 = path(path, p[0].first, p[0].second).value();
auto p2 = path(path, p[1].first, p[1].second).value();
int len1 = p1.size();
int len2 = p2.size();
int over = 0;
for (int i : p1) over += find(p2.begin(), p2.end(), i) != p2.end();
ll res = power(k, n-1);
res -= k * power(k, n-1 - len1) % mod;
res -= k * power(k, n-1 - len2) % mod;
res += k * power(k, n-1 - (len1 + len2 - over)) % mod;
cout << (res % mod + mod) % mod << endl;
};
auto sub3 = [&]() {
vector<int> len(m);
for (int i = 0; i < m; i++)
len[i] = path(path, p[i].first, p[i].second)->size();
ll res = power(k, n - 1);
for (int i = 1; i < (1<<m); i++) {
int cur_len = 0;
int sign = 1;
for (int j = 0; j < m; j++) {
if (i & (1<<j)) {
cur_len += len[j];
sign *= -1;
}
}
res += k * power(k, n - 1 - cur_len) * sign;
res = (res % mod + mod) % mod;
}
cout << (res + mod) % mod << '\n';
};
sub3();
if (m == 1) sub3();
// else if (m == 2) sub2();
else if (n <= 15 && k == 2) sub4();
else {
sub3();
// assert(false);
}
}
Compilation message
Main.cpp: In function 'int main()':
Main.cpp:62:10: warning: variable 'sub1' set but not used [-Wunused-but-set-variable]
62 | auto sub1 = [&]() {
| ^~~~
Main.cpp:67:10: warning: variable 'sub2' set but not used [-Wunused-but-set-variable]
67 | auto sub2 = [&]() {
| ^~~~
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
0 ms |
212 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
0 ms |
212 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
1 ms |
212 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
1 ms |
212 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
0 ms |
212 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
