Submission #1111241

#	Time	Username	Problem	Language	Result	Execution time	Memory
1111241		Thunnus	Amusement Park (CEOI19_amusementpark)	C++17	100 / 100	2229 ms	10976 KiB

amusementpark

#include<bits/stdc++.h>
using namespace std;
using i64 = long long;
#define int i64
#define vi vector<int>
#define vvi vector<vi>
#define vb vector<bool>
#define pii pair<int, int>
#define fi first
#define se second
#define sz(x) (int)(x).size()

const int MAXN = 18;
const int MOD = 998244353;
int adj[1 << MAXN], popcnt[1 << MAXN], pie[1 << MAXN], nodeid[1 << MAXN], f[1 << MAXN];
bool indepset[1 << MAXN];

signed main(){
    ios_base::sync_with_stdio(false); cin.tie(0);
    int n, m, u, v;
    cin >> n >> m;
    for(int i = 0; i < m; i++){
        cin >> u >> v;
        u--, v--;
        adj[u] |= (1ll << v);
        adj[v] |= (1ll << u);
    }
    for(int i = 0; i < n; i++){
        nodeid[1ll << i] = i;
    }
    for(int i = 0; i < (1ll << n); i++){
        popcnt[i] = popcnt[i >> 1] + (i & 1);
        pie[i] = (popcnt[i] % 2) * 2 - 1;
    }

    indepset[0] = true;
    for(int i = 1; i < (1ll << n); i++){
        if(indepset[i & (i - 1)] && ((adj[nodeid[i & -i]] & (i & (i - 1))) == 0)){ // deciding whether the subset including the nodes in the mask id DAG
            indepset[i] = true;
        }
    }

    f[0] = 1;
    for(int i = 1; i < (1ll << n); i++){ // O(3^n)
        for(int j = i; j; j = (j - 1) & i){
            if(indepset[j]){
                f[i] = (f[i] + pie[j] * f[i ^ j]) % MOD; // PIE
            }
        }
    }
    f[(1 << n) - 1] = (f[(1 << n) - 1] + MOD) % MOD;
	cout << f[(1 << n) - 1] * m % MOD * ((MOD + 1) / 2) % MOD; // (MODE + 1) / 2 is the modular inverse of 2.
	return 0;
}

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