Submission #1259626

#	Time	Username	Problem	Language	Result	Execution time	Memory
1259626		nqknht	Potemkin cycle (CEOI15_indcyc)	C++20	10 / 100	116 ms	54340 KiB

indcyc

#include <bits/stdc++.h>
#define ll long long
// CODE NAY KO PHAI DO TOI CODE CHI NOP DE THU TRUONG HOP SAI. Original Author: anha3k25cvp
#define dl double
#define st first
#define nd second
#define II pair<int, int>

using namespace std;

const int N = 1 + 1e3;
const int inf = 7 + 1e9;

struct Edge
{
    int u, v;
};

int s = 0, t = -1;
vector<Edge> e;
vector<int> deg, vis, p;
vector<vector<int>> adj;

void dfs(int u)
{
    if (s != 0)
        return;
    vis[u] = 1;
    // cout << u << "\n";
    for (int v : adj[u])
    {
        if (!vis[v])
        {
            p[v] = u;
            // cout << "- " << u << ' ' << v << '\n';
            dfs(v);
            if (s == -1)
                return;
            if (s == v)
            {
                cout << (v % 2 == 0 ? e[(v / 2)].u : e[(v / 2)].v) << " " ;
                s = -1;
                return;
            }
            else if (s > 0)
            {
                cout << (v % 2 == 0 ? e[(v / 2)].u : e[(v / 2)].v) << " ";
                return;
            }
        }
        else if (vis[v] == 1)
        {
            s = v;
            // cout << s << "\n";
            return;
        }
        if (s >= 0)
            return;
    }
    vis[u] = 2;
}

int main()
{
#define TASKNAME ""
    ios_base ::sync_with_stdio(0);
    cin.tie(0);
    if (fopen(TASKNAME ".inp", "r"))
    {
        freopen(TASKNAME ".inp", "r", stdin);
        freopen(TASKNAME ".out", "w", stdout);
    }
    int n, m;
    cin >> n >> m;
    e.resize(2 * m + 2);
    vector<vector<int>> f(n + 1, vector<int>(n + 1, 0));
    for (int i = 1; i <= m; i++)
    {
        cin >> e[i].u >> e[i].v;
        f[e[i].u][e[i].v] = i * 2;
        f[e[i].v][e[i].u] = i * 2 + 1;
    }
    adj.resize(2 * m + 2);
    for (int i = 1; i <= m; i++)
    {
        int u = e[i].u, v = e[i].v;
        for (int w = 1; w <= n; w++)
            if (w != u && w != v)
            {
                if (f[v][w] && !f[u][w])
                    adj[i * 2].push_back(f[v][w]);
                if (f[u][w] && !f[v][w])
                    adj[i * 2 + 1].push_back(f[u][w]);
            }
    }
    // for (int i = m; i > 0; i--)
    // {
    //     e[i * 2] = e[i];
    //     e[i * 2 + 1] = {e[i].v, e[i].u};
    // }
    vis.assign(2 * m + 2, 0);
    p.assign(2 * m + 2, 0);
    for (int i = 2; i < m * 2 + 2; i++)
        if (!vis[i])
        {
            dfs(i);
            if (s != -1 && s > 0)
            {
                cout << (i % 2 == 0 ? e[i / 2].u : e[i / 2].v) << " ";
                return 0;
            }
            if (s != 0)
                return 0;
        }
    if (s < 0)
    {
        cout << "no";
        return 0;
    }
    // vector <int> c;
    // c.push_back(e[s].u);
    // while (s != t) {
    //     s = p[s];
    //     c.push_back(e[s].u);
    // }
    // for (int i = (int)c.size() - 1; i >= 0; i --)
    //     for (int j = i + 3; j < c.size(); j ++)
    //         if (f[c[i]][c[j]]) {
    //             for (int u = i; u <= j; u ++)
    //                 cout << c[u] << ' ';
    //             return 0;
    //         }
    return 0;
}

Compilation message (stderr)

indcyc.cpp: In function 'int main()':
indcyc.cpp:70:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   70 |         freopen(TASKNAME ".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
indcyc.cpp:71:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   71 |         freopen(TASKNAME ".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 10
• Subtask 2: 10 / 10
• Subtask 3: 0 / 10
• Subtask 4: 0 / 10
• Subtask 5: 0 / 10
• Subtask 6: 0 / 10
• Subtask 7: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10
• Subtask 10: 0 / 10