Submission #314912

#	Time	Username	Problem	Language	Result	Execution time	Memory
314912		mohamedsobhi777	Potemkin cycle (CEOI15_indcyc)	C++14	30 / 100	1093 ms	14328 KiB

indcyc

#include <bits/stdc++.h>

#pragma GCC optimize("-Ofast")
//#pragma GCC optimize("trapv")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,sse4.2,popcnt,abm,mmx,avx2,tune=native")
#pragma GCC optimize("-ffast-math")
#pragma GCC optimize("-funroll-loops")

#define I inline void
#define S struct
#define vi vector<int>
#define vii vector<pair<int, int>>
#define pii pair<int, int>
#define pll pair<ll, ll>

using namespace std;
using ll = long long;
using ld = long double;

const int N = 1000 + 7, mod = 1e9 + 7;
const ll inf = 2e18;

// How interesting!

int n, m, t;
int st[N], prv[N];
vector<int> adj[N];
map<pii, int> ed;

void cycle(vector<int> v, int x, int y)
{
        int k = 0;
        while (x != y && k++ < 50)
        {
                v.push_back(x);
                x = prv[x];
        }
        int sz = (int)v.size();
        if (sz < 4)
                return;
        bool bad = 0;
        for (int i = 0; i < sz; ++i)
        {
                for (int j = 0; j < n; ++j)
                {
                        if (i == j || (i + 1) % sz == j || (j + 1) % sz == i)
                                continue;
                        if (ed[{v[i], v[j]}])
                        {
                                bad = 1;
                                break;
                        }
                }
        }
        if (!bad)
        {
                for (auto u : v)
                        cout << u << " ";
                exit(0);
        }
}

void dfs(int x, int p)
{
        st[x] = ++t;
        prv[x] = p;
        for (auto u : adj[x])
        {
                if (u == p)
                        continue;
                if (st[u])
                {
                        if (st[u] < st[x])
                        {
                                cycle({u}, x, u);
                        }
                        else
                        {
                                cycle({x}, u, x);
                        }
                }
                else
                {
                        dfs(u, x);
                }
        }
}

int main()
{
        ios_base::sync_with_stdio(0);
        cin.tie(0);
        //freopen("in.in", "r", stdin);
        cin >> n >> m;
        for (int i = 0; i < m; ++i)
        {
                int u, v;
                cin >> u >> v;
                adj[u].push_back(v);
                adj[v].push_back(u);
                ed[{u, v}] = ed[{v, u}] = 1;
        }
        for (int i = 1; i <= n; ++i)
        {
                memset(st, 0, sizeof st);
                memset(prv, 0, sizeof prv);
                t = 0;
                dfs(i, i);
        }
        cout << "no";
        return 0;
}

/*
        - bounds sir (segtree = 4N, eulerTour = 2N, ...)
        - a variable defined twice?
        - will overflow?
        - is it a good complexity?
        - don't mess up indices (0-indexed vs 1-indexed)
        - reset everything between testcases. 
*/

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 0 / 10
• Subtask 4: 10 / 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