Submission #1003647

#	Time	Username	Problem	Language	Result	Execution time	Memory
1003647		GrindMachine	Amusement Park (CEOI19_amusementpark)	C++17	42 / 100	444 ms	1048576 KiB

amusementpark

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) (int)a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x,y) ((x+y-1)/(y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl

#define rep(i,n) for(int i = 0; i < n; ++i)
#define rep1(i,n) for(int i = 1; i <= n; ++i)
#define rev(i,s,e) for(int i = s; i >= e; --i)
#define trav(i,a) for(auto &i : a)

template<typename T>
void amin(T &a, T b) {
    a = min(a,b);
}

template<typename T>
void amax(T &a, T b) {
    a = max(a,b);
}

#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 42
#endif

/*

read the solution a long time ago and remember some ideas from there

*/

const int MOD = 1e9 + 7;
const int N = 20 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;

vector<pll> adj[N];

void solve(int test_case)
{
    ll n,m; cin >> n >> m;
    rep1(i,m){
        ll u,v; cin >> u >> v;
        u--, v--;
        adj[u].pb({v,0}), adj[v].pb({u,1});
    }

    ll dp[1<<n][1<<n];
    memset(dp,0,sizeof dp);
    dp[0][0] = 1;

    rep(mask,1<<n){
        rep(bad,1<<n){
            if(!dp[mask][bad]) conts;
            rep(u,n){
                if(mask&(1<<u) or bad&(1<<u)) conts;
                int mask2 = mask|(1<<u);
                int bad2 = bad;
                bad2 |= (1<<u)-1;
                for(auto [v,t] : adj[u]){
                    if(mask&(1<<v)) conts;
                    if(bad2&(1<<v)){
                        bad2 ^= (1<<v);
                    }
                }

                dp[mask2][bad2] += dp[mask][bad];
                dp[mask2][bad2] %= MOD;
            }
        }
    }

    ll ans = 0;
    rep(bad,1<<n){
        ans += dp[(1<<n)-1][bad];
        ans %= MOD;
    }

    ans = ans*m%MOD*((MOD+1)/2)%MOD;
    cout << ans << endl;
}

int main()
{
    fastio;

    int t = 1;
    // cin >> t;

    rep1(i, t) {
        solve(i);
    }

    return 0;
}

• Subtask 1: 7 / 7
• Subtask 2: 12 / 12
• Subtask 3: 23 / 23
• Subtask 4: 0 / 21
• Subtask 5: 0 / 37