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68 lines
1.5 KiB
68 lines
1.5 KiB
#include <bits/stdc++.h>
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using namespace std;
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const int N = 20, M = N << 1;
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#define int long long
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// 链式前向星
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int e[M], h[N], idx, w[M], ne[M];
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void add(int a, int b) {
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e[idx] = b, ne[idx] = h[a], h[a] = idx++;
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}
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int g[N][N];
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int f[N][N];
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int st[N];
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int flag[N];
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int n, m;
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// https://blog.csdn.net/Emm_Titan/article/details/123597082
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void dfs(int u) {
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st[u] = 1;
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for (int i = 1; i <= n; i++) f[u][i] = flag[i] ^ 1;
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for (int i = h[u]; ~i; i = ne[i]) {
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int v = e[i];
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if (st[v]) continue;
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dfs(v);
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for (int i = 1; i <= n; i++) {
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if (flag[i]) continue;
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int sum = 0;
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for (int j = 1; j <= n; j++)
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if (g[i][j] and !flag[j]) sum += f[v][j];
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f[u][i] *= sum;
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}
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}
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}
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signed main() {
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memset(h, -1, sizeof h);
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cin >> n >> m;
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int a, b;
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for (int i = 1; i <= m; i++) {
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cin >> a >> b;
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g[a][b] = g[b][a] = 1;
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}
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for (int i = 1; i < n; i++) {
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cin >> a >> b;
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add(a, b), add(a, b);
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}
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int ans = 0;
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for (int s = 0; s < (1 << n); s++) {
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for (int i = 0; i < n; i++)
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flag[i + 1] = s >> i & 1;
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// 多次调用dfs
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memset(st, 0, sizeof st);
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dfs(1);
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int sum = 0;
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for (int i = 1; i <= n; i++) sum += f[1][i];
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if (__builtin_popcount(s) & 1) // 似乎是查询s里有多少个数字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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printf("%lld\n", ans);
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}
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