Submission #1040175

#	Time	Username	Problem	Language	Result	Execution time	Memory
1040175		ef10	Amusement Park (CEOI19_amusementpark)	C++17	100 / 100	2883 ms	4772 KiB

amusementpark

// Source: https://usaco.guide/general/io

#include <bits/stdc++.h>
using namespace std;

#define LL long long
#define MODULE 998244353

int N,M;
int adj[20];
//map<int,int> ni;
int sign[1<<18];
int popc[1<<18];
bool indp[1<<18];
LL dp[1<<18];

LL exp(LL a, LL b) {
		if (a==0) return 0;
        if (b == 0) return 1;
        LL ret = exp(a, b/2);
        ret = ret * ret;
        ret %= MODULE;
        if (b % 2) {
                ret *= a;
                ret %= MODULE;
        }
        return ret;
}

LL inv(LL x) {
        return exp(x, MODULE-2);
}

int main() {
	cin >> N >> M;
	for (int i = 0; i < M; i++) {
		int a,b; cin >> a >> b; a--;b--;
		adj[a] |= (1 << b);
		adj[b] |= (1<<a);
	}
	/*cout << "adj: " << endl;
	for (int i = 0; i < N; i++) {
		cout << adj[i] << endl;
	}*/
	for (int i = 0; i < (1<<N); i++) {
		popc[i] = popc[i>>1] + (i&1);
		sign[i] = (popc[i] % 2) ? (1) : (-1);
	}
	indp[0] = true;
	for (int i = 1; i < (1<<N); i++) {
		for (int j = 0; j < N; j++) {
			if (!(i&(1<<j))) continue;
			if (!indp[i&~(1<<j)]) continue;
			if ((adj[j]&(i&~(1<<j))) == 0) {
				indp[i] = true;
			}
		}
		/*if (indp[i]) {
			cout << "indp: " << i << endl;
		}*/
	}

	dp[0] = 1;
	for (int i = 1; i < (1<<N); i++) {
		for (int j = i; j; j=(j-1)&i) {
			if (!indp[j]) continue;
			if (dp[i&~j]==0) continue;
			dp[i]+=dp[i&~j]*sign[j];
			dp[i]%=MODULE;
			dp[i]=(dp[i]+MODULE)%MODULE;
		}
		//cout << "dp["<<i<<"] = " << dp[i] << endl;
	}
	LL res = dp[(1<<N)-1];
	//cout << res << endl;
	res *= M;
	res %= MODULE;
	res *= inv(2);
	res %= MODULE;
	cout << res << endl;
}

• Subtask 1: 7 / 7
• Subtask 2: 12 / 12
• Subtask 3: 23 / 23
• Subtask 4: 21 / 21
• Subtask 5: 37 / 37