mirror of
https://git.sb/baoshuo/OI-codes.git
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86 lines
1.5 KiB
C++
86 lines
1.5 KiB
C++
#include <iostream>
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#include <cstring>
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#include <vector>
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using std::cin;
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using std::cout;
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const char endl = '\n';
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const int N = 20;
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int n, m;
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long long f[N][N], ans;
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bool map[N][N], vis[N];
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std::vector<int> g[N];
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void dfs(int u, int fa) {
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for (int i = 1; i <= n; i++) {
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if (vis[i]) f[u][i] = 1;
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}
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for (int v : g[u]) {
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if (v == fa) continue;
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dfs(v, u);
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for (int i = 1; i <= n; i++) {
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if (!vis[i]) continue;
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long long t = f[u][i];
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for (int j = 1; j <= n; j++) {
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if (!vis[j] || !map[i][j]) continue;
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f[u][i] += t * f[v][j];
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}
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}
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}
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}
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int main() {
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std::ios::sync_with_stdio(false);
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cin.tie(nullptr);
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cin >> n >> m;
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for (int i = 1, u, v; i <= m; i++) {
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cin >> u >> v;
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map[u][v] = map[v][u] = true;
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}
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for (int i = 1, u, v; i < n; i++) {
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cin >> u >> v;
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g[u].emplace_back(v);
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g[v].emplace_back(u);
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}
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for (int s = 0; s < 1 << n; s++) {
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memset(f, 0x00, sizeof(f));
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memset(vis, 0x00, sizeof(vis));
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for (int i = 1; i <= n; i++) {
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if ((s >> (i - 1)) & 1) vis[i] = true;
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}
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dfs(1, -1);
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long long sum = 0;
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for (int i = 1; i <= n; i++) {
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sum += f[1][i];
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}
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if ((n - __builtin_popcount(s)) & 1) {
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ans -= sum;
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} else {
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ans += sum;
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}
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}
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cout << ans << endl;
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return 0;
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}
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