Submission #1176373

#	Time	Username	Problem	Language	Result	Execution time	Memory
1176373		anha3k25cvp	Potemkin cycle (CEOI15_indcyc)	C++20	50 / 100	249 ms	92176 KiB

indcyc

#include <bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#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 node = 0;
vector <Edge> e;
vector <int> num, low, used, ans;
vector <vector <int>> adj;
stack <int> q;

void dfs(int u) {
    num[u] = low[u] = ++ node;
    q.push(u);
    for (int v : adj[u]) {
        if (!num[v]) {
            dfs(v);
            low[u] = min(low[u], low[v]);
        }
        else
            low[u] = min(low[u], num[v]);
    }
    if (num[u] == low[u]) {
        int v = 0;
        vector <int> c;
        while (v != u) {
            v = q.top(); q.pop();
            num[v] = low[v] = inf;
            c.push_back(v);
        }
        if (c.size() > 1)
            ans = c;
    }
}

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);
    adj.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;
    }
    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[2 * i] = e[i];
        e[2 * i + 1] = {e[i].v, e[i].u};
    }
    num.assign(2 * m + 2, 0);
    low.assign(2 * m + 2, 0);
    used.assign(2 * m + 2, 0);
    for (int i = 2; i < 2 * m + 2; i ++)
        if (!num[i])
            dfs(i);
    if (ans.empty()) {
        cout << "no";
        return 0;
    }
    for (int i : ans)
        cout << e[i].u << ' ';
    return 0;
}

Compilation message (stderr)

indcyc.cpp: In function 'int main()':
indcyc.cpp:53:17: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   53 |         freopen (TASKNAME".inp", "r", stdin);
      |         ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
indcyc.cpp:54:17: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   54 |         freopen (TASKNAME".out", "w", stdout);
      |         ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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