Submission #115896

#	Time	Username	Problem	Language	Result	Execution time	Memory
115896		rajarshi_basu	Potemkin cycle (CEOI15_indcyc)	C++14	100 / 100	698 ms	6400 KiB

indcyc

#include <iostream>
#include <vector>
#include <set>
#include <iomanip>
#include <algorithm>
#include <functional>
#include <stdio.h>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <fstream>
#include <complex>
#include <stack>
#include <set>

#define FOR(i,n) for(int i=0;i<n;i++)
#define FORE(i,a,b) for(int i=a;i<=b;i++)
#define ll long long int
#define vi vector<int>
#define ii pair<int,int>
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define pll pair<ll,ll>
#define cd complex<double> 
#define ld long double
#define pld pair<ld,ld>
#define iii pair<ii,int>

using namespace std;

const int INF = 1e9+10;
const int MAXN = 1000+10;

int n,m;
bool mat[MAXN][MAXN];
int vis[MAXN][MAXN];
bool dvis[MAXN][MAXN];
bool validEdge[MAXN][MAXN];

stack<ii> cyc;
set<int> allnode;
bool done = 0;

inline bool isok(int a,int b,int c){
	return (!(mat[a][b] and mat[b][c] and mat[a][c]));
}

void dfs1(ii node){
	if(done)return;
	cyc.push(node);
	//cout << node.ff << " " << node.ss << endl;
	if(vis[node.ff][node.ss]){
		// we got our cycle
		if(cyc.size() < 3){
			cyc.pop();
			return;
		}
		allnode.insert(node.ff);
		allnode.insert(node.ss);
		cyc.pop();
		while(cyc.size() > 0){
			ii x = cyc.top();cyc.pop();
			//if(x.ff == x.ss)break;
		//	cout <<x.ff << ' ' << x.ss << endl;
			validEdge[x.ff][x.ss] = validEdge[x.ss][x.ff] = 1;
			allnode.insert(x.ff);
			allnode.insert(x.ss);	
			if(x.ff == node.ff and x.ss == node.ss)break;
		}	
		done = 1;
		return;
	}

	vis[node.ff][node.ss] = 1;
	//vis[node.ss][node.ff] = 1;
					

	FOR(nxt,n){
		if(nxt == node.ff or node.ss == nxt)continue;
		if(!mat[nxt][node.ss])continue;
		if(isok(node.ff,node.ss,nxt)){
			// this is a valid edge;
			if(vis[node.ss][nxt] == 2)continue;
			dfs1({node.ss,nxt});
			//vis[node.ff][node.ss] = 0;

			if(done)return;
		}

	}
	vis[node.ff][node.ss] = 2;
	if(cyc.size()>0)cyc.pop();
}

bool impNode[MAXN];
bool vis2[MAXN];
stack<int> st;
vector<int> cc;
void dfs2(int node,int p = -1){
	if(done)return;
	st.push(node);
	//cout << node << endl;
  	vis2[node] = 1;
	FOR(i,n){
		if(node == i)continue;
		if(p == i)continue;
		if(done)return;
		
		if(mat[node][i] and vis2[i] and impNode[i] and !validEdge[node][i]){
			//st.pop();
			while(!st.empty()){
				int x = st.top();st.pop();
				cc.pb(x);
				if(x == i)break;
			}
			done = 1;
			return;
		}

		if(validEdge[node][i]){
			if(vis2[i]){
				//st.pop();

				while(!st.empty()){
					int x = st.top();st.pop();
					cc.pb(x);
					if(x == i)break;
				}
				done = 1;
			}else{
				dfs2(i,node);	
			}
			
		}
		if(done)return;
	}
	if(st.size()>0)st.pop();
}

int main(){
	cin >> n >> m;
	FOR(i,n)FOR(j,n)mat[i][j] = validEdge[i][j] = vis[i][j] = 0;
	
	FOR(i,m){
		int a,b;
		cin >> a >> b;
		a--;b--;
		mat[a][b] = mat[b][a] = 1;
	}
	// input done
	FOR(i,n){
		FOR(j,n)
			if(!vis[i][j] and i != j and mat[i][j])
				dfs1({i,j});

		while(!cyc.empty())cyc.pop();
	}
	if(!done){
		cout << "no" << endl;
		return 0;
	}

	int x;
	for(auto e:allnode){
		impNode[e] = 1;
		x = e;
	}
	/*
	cout << endl;
	for(auto e:allnode){
		cout << e << endl;
	}
	cout << endl;
*/
	FOR(i,n){
		FOR(j,n){
			if(validEdge[i][j] and !mat[i][j])return -1;
		}
	}

	done = 0;
	
	dfs2(x);
	
	if(cc.empty()){
		cout << "no" << endl;
	}else{
		FOR(i,cc.size()){

			//if(!mat[cc[(i+cc.size()-1)%cc.size()]][cc[i]])return -1;
		}
		for(auto e:cc){
			cout << e+1 << " ";
		}

		cout << endl;
	}
	return 0;
}

Compilation message (stderr)

indcyc.cpp: In function 'int main()':
indcyc.cpp:145:58: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
  FOR(i,n)FOR(j,n)mat[i][j] = validEdge[i][j] = vis[i][j] = 0;
                                                ~~~~~~~~~~^~~
indcyc.cpp:17:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 #define FOR(i,n) for(int i=0;i<n;i++)
indcyc.cpp:191:7:
   FOR(i,cc.size()){
       ~~~~~~~~~~~              
indcyc.cpp:191:3: note: in expansion of macro 'FOR'
   FOR(i,cc.size()){
   ^~~
indcyc.cpp:186:6: warning: 'x' may be used uninitialized in this function [-Wmaybe-uninitialized]
  dfs2(x);
  ~~~~^~~

• 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: 10 / 10
• Subtask 8: 10 / 10
• Subtask 9: 10 / 10
• Subtask 10: 10 / 10