Submission #245390

#	Time	Username	Problem	Language	Result	Execution time	Memory
245390		lyc	Potemkin cycle (CEOI15_indcyc)	C++14	60 / 100	1092 ms	3908 KiB

indcyc

#include <bits/stdc++.h>
using namespace std;

#define TRACE(x) cerr << #x << " :: " << x << endl
#define _ << " " <<
#define SZ(x) (int)(x).size()
#define ALL(x) (x).begin(),(x).end()
#define FOR(i,a,b) for(int i=(a);i<=(b);++i)
#define RFOR(i,a,b) for (int i=(a);i>=(b);--i)
using ii = pair<int,int>;

const int mxN = 1e3+5;
const int mxR = 1e5+5;

int N, R;
vector<int> al[mxN], al2[mxN];
bool am[mxN][mxN];

bool block[mxN];
vector<int> ans;

struct UFDS {
    int p[mxN], s[mxN];
    UFDS() { FOR(i,1,N) p[i] = i, s[i] = 1; }
    int finds(int i) { return (p[i] == i) ? i : (p[i] = finds(p[i])); }
    bool sames(int i, int j) { return finds(i) == finds(j); }
    bool unions(int i, int j) {
        int x = finds(i), y = finds(j);
        if (x == y) return 0;
        if (s[x] < s[y]) swap(x,y);
        p[y] = x, s[x] += s[y];
        return 1;
    }
};

int dist[mxN], pa[mxN];
queue<int> q;

void bfs(int s) {
    memset(dist,-1,sizeof dist);
    memset(pa,-1,sizeof pa);
    dist[s] = 0; q.push(s);
    while (!q.empty()) {
        int u = q.front(); q.pop();
        for (int v : al[u]) if (!block[v] && dist[v] == -1) {
            dist[v] = dist[u]+1, pa[v] = u;
            q.push(v);
        }
    }
}

bool solve(int s) {
    block[s] = 1;
    for (int v : al[s]) block[v] = 1;

    UFDS uf;
    FOR(u,1,N) for (int v : al[u]) if (!block[u] && !block[v]) {
        uf.unions(u,v);
    }

    FOR(u,1,N) al2[u].clear();
    FOR(u,1,N){
        int x = uf.finds(u);
        for (int v : al[u]) {
            int y = uf.finds(v);
            if (x != y) {
                al2[x].push_back(y);
                al2[y].push_back(x);
            }
        }
    }

    FOR(i,0,SZ(al[s])-1){
        int u = al[s][i];
        FOR(j,i+1,SZ(al[s])-1){
            int v = al[s][j];
            if (!am[u][v]) block[v] = 0;
        }

        bfs(u);
        FOR(j,i+1,SZ(al[s])-1){
            int v = al[s][j];
            if (!am[u][v]) {
                if (dist[v] != -1) {
                    for (int x = v; x != -1; x = pa[x]) ans.push_back(x);
                    ans.push_back(s);
                    return true;
                }
                block[v] = 1;
            }
        }
    }

    block[s] = 0;
    for (int v : al[s]) block[v] = 0;
    return false;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    cin >> N >> R;
    FOR(i,1,R){
        int A, B; cin >> A >> B;
        al[A].push_back(B);
        al[B].push_back(A);
        am[A][B] = am[B][A] = 1;
    }

    FOR(i,1,N){
        if (solve(i)) {
            for (int x : ans) {
                cout << x << ' ';
            }
            cout << '\n';
            return 0;
        }
    }
    cout << "no" << '\n';
}

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