Submission #519715

#	Time	Username	Problem	Language	Result	Execution time	Memory
519715		Monarchuwu	Amusement Park (CEOI19_amusementpark)	C++17	0 / 100	1 ms	256 KiB

amusementpark

#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;
typedef long long ll;

typedef pair<int, int> pii;
#define ff first
#define ss second

const int N = 20, M = 400;
int n, m;
pii edge[N];

vector<int> g[N];
void loadGraph(int mask) {
    for (int i = 1; i <= n; ++i) g[i].clear();
    for (int i = 0; i < m; ++i)
        if (mask >> i & 1)
            g[edge[i].ss].push_back(edge[i].ff);
        else g[edge[i].ff].push_back(edge[i].ss);
}

int vis[N];
bool dfs(int u, int tme) {
    vis[u] = tme;
    for (int v : g[u]) {
        if (!vis[v]) dfs(v, tme);
        else if (vis[v] == tme) return true;
    }
    return false;
}
bool check() {
    fill(vis + 1, vis + n + 1, 0);
    for (int i = 1; i <= n; ++i)
        if (!vis[i] && dfs(i, i)) return false;
    return true;
}

int lg[N];
int main() {
    cin.tie(NULL)->sync_with_stdio(false);
    cin >> n >> m;
    for (int i = 0; i < m; ++i)
        cin >> edge[i].ff >> edge[i].ss;

    int cnt(0);
    for (int mask = 0; mask < (1 << m); ++mask) {
        lg[mask] = lg[mask >> 1] + (mask & 1);
        loadGraph(mask);
        if (check()) cnt += lg[mask];
    }
    cout << cnt << '\n';
}
/**  /\_/\
 *  (= ._.)
 *  / >0  \>1
**/

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