Submission #244569

#	Time	Username	Problem	Language	Result	Execution time	Memory
244569		oolimry	Potemkin cycle (CEOI15_indcyc)	C++14	30 / 100	1098 ms	2552 KiB

indcyc

//HAPPY BIRTHDAY!!!
#include <bits/stdc++.h>
using namespace std;
typedef pair<int,int> ii;

int depth[1005];
vector<int> adj[1005];
vector<int> paths[1005];
vector<ii> backs;
void dfs(int u){
	for(int v : adj[u]){
		if(depth[v] != 0){
			if(depth[v] < depth[u]-1){ ///back edge
				int dist = depth[u] - depth[v];
				backs.push_back(ii(dist, u));
			}
		}
		else{
			depth[v] = depth[u] + 1;
			paths[v].push_back(u);
			dfs(v);
		}
	}
}

signed main(){
	ios_base::sync_with_stdio(false); cin.tie(0);
	
	int n, m; cin >> n >> m;
	
	
	if(n <= 10){
		set<ii> edges;
		for(int i = 0;i < m;i++){
			int a, b; cin >> a >> b;
			edges.insert(ii(a,b));
			edges.insert(ii(b,a));
		}
		
		vector<int> v;
		for(int i = 1;i <= n;i++) v.push_back(i);
		
		do{
			
			for(int sz = 4;sz <= n;sz++){
				int can = true;
				for(int i = 0;i < sz;i++){
					int a = v[i];
					int b = v[(i+1)%sz];
					
					if(edges.find(ii(a,b)) == edges.end()){
						can = false;
						break;
					}
				}
				
				int cnt = 0;
				for(int i = 0;i < sz;i++){
					for(int j = 0;j < sz;j++){
						int a = v[i];
						int b = v[j];
						if(edges.find(ii(a,b)) != edges.end()) cnt++;
					}
				}
				
				if(cnt == 2*sz && can){
					for(int i = 0;i < sz;i++) cout << v[i] << " ";
					return 0;
				}
			}
		} while(next_permutation(v.begin(),v.end()));
		
		cout << "no";
		return 0;
	}
	
	for(int i = 0;i < m;i++){
		int a, b; cin >> a >> b;
		adj[a].push_back(b);
		adj[b].push_back(a);
	}
	
	for(int i = 1;i <= n;i++){
		if(depth[i] != 0) continue; ///visited;
		backs.clear();
		
		depth[i] = 1;
		dfs(i);
		
		sort(backs.begin(), backs.end());
		for(ii e : backs){
			//cout << e.first << " " << e.second << ":" << endl;
			int u = e.second;
			int targetDepth = depth[u] - e.first;
			//cout << targetDepth << "\n";
			
			vector<int> P;
			while(depth[u] != targetDepth){
				P.push_back(u);
				
				for(int i = (int) (paths[u].size()-1);i >= 0;i--){
					int v = paths[u][i];
					//cout << u << " " << v << endl;
					
					if(depth[v] >= targetDepth){
						u = v;
						break;
					}
				}
			}
			
			P.push_back(u);
			
			if((int) P.size() >= 3){
				for(int x : P) cout << x << " ";
				return 0;
			}
			else{
				paths[e.second].push_back(u);
			}
		
		}
	}
	
	cout << "no";
}

• 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