detect cycle directed graph.cpp

/* https://sapphireengine.com/@/6tfphj */
/* https://cses.fi/problemset/task/1678 */
#include<iostream>
using namespace std;

int graph[100][100];
int n;

bool dfs( int node , bool *visited , bool *inloop , int &prev ){
	visited[node] = 1;
	inloop[node] = 1;
    for(int i=0;i<n;i++){
	    if( graph[node][i]){  	
	      	if(!visited[i]){
	      		if(dfs( i , visited , inloop , prev)){
	      	 	 	
				    if(i==prev)
	      	 	 	    cout<<i<<" " , prev=-1;
	      	 	    else if (prev!=-1)
					    cout<<i<<" ";
						    
	      	 	    return true;
	      	    }
			}
			else if ( inloop[i] ){
				    prev=i;
			 	    return true;
		    }  
	    }
    }

    inloop[node]=0;  
	return false;			 
}

bool checkCycle (bool *visited){
	int prev = -1;
	bool inloop[n] = {false};
	
	for(int i=0; i<n; i++)
	    if( !visited[i] && dfs(i,visited, inloop, prev))
	        return true;

	return false; 
}

int main(){
	// Input nodes
	cin>>n;
	for(int i=0;i<n;i++)
	    for(int j=0;j<n;j++)
	        graph[i][j]=0;
	 
	// Input Edges 
	int t; 
	cin>>t;   
	int x,y;
	for(int i=0;i<t;i++){
		cin>>x>>y;
		graph[x][y]=1;
	}

	bool visited[n] = {false};

	cout<<checkCycle(visited)<<endl;     
	
	return 0;
}