Submission #34673

#	Time	Username	Problem	Language	Result	Execution time	Memory
34673		mohammad_kilani	Potemkin cycle (CEOI15_indcyc)	C++14	40 / 100	1000 ms	4012 KiB

indcyc

#include <bits/stdc++.h>
using namespace std;
#define mod 1000000007
#define oo 2000000000
const int N =1010 , M = 100010;
bitset< N > con[N] , con2[N] , can2; 
int n, m , vi = 0 , vis[N] , pre[N] , prnt[N] , a , b;
vector<int> g[N];
pair<int,int> edges[M];

int find(int u){
	return (u == prnt[u] ? u : prnt[u] = find(prnt[u]));
}

bool BFS(int s,int e){
	vi++;
	queue < pair<int,int> > q;
	vis[s] = vi;
	pre[s] = s;
	for(int i=0;i<g[s].size();i++){
		int node = g[s][i];
		if(node == e || (con[node][e])) continue;
		vis[node] = vi;
		q.push(make_pair(node,s));
	}
	while(!q.empty()){
		int node = q.front().first;
		int last = q.front().second;
		q.pop();
		pre[node] = last;
		if(node == e) return true;
		for(int i=0;i<g[node].size();i++){
			int newnode = g[node][i];
			if(vis[newnode] == vi || (con[newnode][s] && con[newnode][e])) continue;
			vis[newnode] = vi;
			q.push(make_pair(newnode,node));
		}
	}
	return false;
}

void make(int u ,int v){
	BFS(u,v);
	int cur = v;
	while(pre[cur] != cur){
		printf("%d ",cur);
		cur = pre[cur];
	}
	printf("%d\n",cur);
	exit(0);
}

int main() {
	//freopen("in.txt","r",stdin);
	scanf("%d%d",&n,&m);
	for(int i=0;i<m;i++){
		int u ,v;
		scanf("%d%d",&u,&v);
		g[u].push_back(v);
		g[v].push_back(u);
		con[u][v] = con[v][u] = true;
		edges[i] = make_pair(u,v);
	}
	
	for(int i=1;i<=n;i++){
		for(int i=1;i<=n;i++){
			prnt[i] = i;
			can2[i] = false;
		}
		for(int j=0;j<m;j++){
			if(edges[j].first == i || edges[j].second == i) continue;
			a = find(edges[j].first);
			b = find(edges[j].second);
			if(a == b) continue;
			if((con[a][i] && con[b][i]) || (!con[a][i] && !con[b][i])){
				prnt[a] = b;
			}
		}
		for(int j=0;j<m;j++){
			if(edges[j].first == i || edges[j].second == i) continue;
			a = find(edges[j].first);
			b = find(edges[j].second);
			if(a == b) continue;
			if(con2[a][b]) continue;
			con2[a][b] = con2[b][a] = true;
			if(con[b][i]){
				if(can2[a]){
					make(i,edges[j].second);
				}
				else
					can2[a] = true;
			}
			else{
				if(can2[b]){
					make(i,edges[j].first);
				}
				else
					can2[b] = true;

			}

		}
		for(int j=0;j<m;j++){
			a = find(edges[j].first);
			b = find(edges[j].second);
			con2[a][b] = con2[b][a] = false;
		}
		
	}
	puts("no");
	return 0;
}

Compilation message (stderr)

indcyc.cpp: In function 'bool BFS(int, int)':
indcyc.cpp:20:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<g[s].size();i++){
               ^
indcyc.cpp:32:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<g[node].size();i++){
                ^
indcyc.cpp: In function 'int main()':
indcyc.cpp:55:21: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d",&n,&m);
                     ^
indcyc.cpp:58:22: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d",&u,&v);
                      ^

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