# | Time | Username | Problem | Language | Result | Execution time | Memory |
---|---|---|---|---|---|---|---|
1129965 | mnbvcxz123 | Amusement Park (CEOI19_amusementpark) | C++20 | 0 ms | 0 KiB |
#include<bits/stdc++.h>
using namespace std;
using ll=long long;
const int N = 18;
const int M = 998244353;
int a[N];
bool indepset[1 << N];
int popcnt[1 << N];
int arg[1 << N];
int nodeid[1 << N];
ll dp[1 << N];
int main() {
int n, m;
cin >> n >> m;
for (int i = 1; i <= m; i++) {
int u, v;
cin >> u >> v;
u--;
v--;
a[u] |= 1 << v;
a[v] |= 1 << u;
}
for (int i = 0; i < n; i++) { nodeid[1 << i] = i; }
for (int i = 0; i < (1 << n); i++) {
popcnt[i] = popcnt[i >> 1] + (i & 1);
arg[i] = (popcnt[i] % 2) * 2 - 1;
}
indepset[0] = 1;
for (int i = 1; i < (1 << n); i++) {
if (indepset[i & (i - 1)] && (a[nodeid[i & (-i)]] & (i & (i - 1))) == 0) {
indepset[i] = true;
}
}
f[0] = 1;
for (int i = 1; i < (1 << n); i++) {
for (int j = i; j; j = (j - 1) & i) {
if (indepset[j]) { dp[i] = (dp[i] + arg[j] * dp[i ^ j]) % M; }
}
}
dp[(1 << n) - 1] = (dp[(1 << n) - 1] + M) % M;
cout << dp[(1 << n) - 1] * m % M * ((M + 1) / 2) % M;
return 0;
}