Submission #541636

#	Time	Username	Problem	Language	Result	Execution time	Memory
541636		rainliofficial	Potemkin cycle (CEOI15_indcyc)	C++17	30 / 100	17 ms	10316 KiB

indcyc

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int, int>
#define sz(x) (int)x.size()
#define f first
#define s second

struct edge{
    int from, to;
};

const int MAXN = 1005, MAXR = 1e5+5;
edge allEdges[MAXR];
vector<int> edgeGraph[MAXN], cycle;
int connected[MAXN][MAXN];
bool vis[MAXN][MAXN];
int vis2[MAXR];
int n, r;

void dfs(int at, int pv){
    vis[at][pv] = true; 
    // connect all possible edges
    for (int i=0; i<n; i++){
        if (pv != n && i != at && i != pv && connected[at][i] && !connected[i][pv]){
            assert(connected[pv][at] != 0);
            edgeGraph[connected[pv][at]].push_back(connected[at][i]);
        }
    }
    for (int i=0; i<n; i++){
        if (connected[at][i] && !vis[i][at]){
            dfs(i, at);
        }
    }
}

int dfs2(int at, int id){
    vis2[at] = id;
    for (int i : edgeGraph[at]){
        if (vis2[i] == id){
            cycle.push_back(at);
            return i;
        }
        if (vis2[i] > 0){
            continue;
        }
        int inCycle = dfs2(i, id);
        if (inCycle > 0){
            cycle.push_back(at);
            if (inCycle == at){
                return -1;
            }else{
                return inCycle;
            }
        }else if (inCycle == -1){
            return -1;
        }
    }
    return 0;
}
int main(){
    cin.tie(0); ios_base::sync_with_stdio(0);
    // freopen("file.in", "r", stdin);
    // freopen("file.out", "w", stdout);
    cin >> n >> r;
    for (int i=0; i<r; i++){
        int a, b;
        cin >> a >> b;
        a--; b--;
        allEdges[2*i+1] = {a, b};
        allEdges[2*i+2] = {b, a};
        connected[a][b] = 2*i+1;
        connected[b][a] = 2*i+2;
    }
    dfs(0, n);
    for (int i=1; i<=2*r; i++){
        if (!vis2[i]){
            dfs2(i, i);
        }
        if (!cycle.empty()) {
            break;
        }
    }
    if (cycle.empty()){
        cout << "no" << "\n";
        return 0;
    }
    reverse(cycle.begin(), cycle.end());
    vector<int> ans;
    for (int i=0; i<sz(cycle)-1; i++){
        if (i == 0){
            cout << allEdges[cycle[i]].from+1 << " ";
        }
        cout << allEdges[cycle[i]].to+1 << " ";
    }
}

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