GreyNodes.java

/*   Created by IntelliJ IDEA.
 *   Author: Kshitij Varshney (kshitijvarshne1)
 *   Date: 13-Feb-21
 *   Time: 10:41 AM
 *   File: GreyNodes.java
 */

import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Scanner;

public class GreyNodes {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n= sc.nextInt();
        int [] array= new int[n];
        int [] graph= new int[n+2];
        int [] revGraph= new int[n+2];
        for (int i=0;i<= n+1;i++){
            for (int j=0;j<=n+1;j++){
                int x= sc.nextInt();
                if(x==1) {
                    graph[i] = j;
                    revGraph[j]=i;
                }
            }
        }
        for (int i=0;i<n;i++){
            int x= sc.nextInt();
            array[i]=x;
        }
        boolean [] visited= new boolean[n+2];
        boolean [] recStack= new boolean[n+2];
        for (int i=0;i<n+2;i++){
            visited[i]= false;
            recStack[i]= false;
        }
        for (int i=0;i<n+2;i++){
            if(cycle(i,visited,recStack,graph)){
                System.out.println("True");
                System.exit(0);
            }
        }

        for (int i=0;i<=n+1;i++){
            visited[i]=false;
        }
        dfs(0,graph,visited);
        for (int i=0;i<= n+1;i++){
            if(visited[i]=false){
                System.out.println(i);
                System.out.println("False");
                System.exit(0);
            }
            visited[i]= false;
        }
        dfs(n+1,revGraph,visited);

        for (int i=0;i<=n+1;i++){
            if(visited[i]==false){
                System.out.println("False");
                System.exit(0);

            }
            visited[i]= false;
        }
        System.out.println("True");


    }
    public static boolean cycle(int v, boolean[] visited, boolean[] recStack, int[] graph){
        if(visited[v]==false){
            visited[v]=true;
            recStack[v]=true;
            for(var i: graph){
                if(!visited[i] && cycle(i,visited,recStack,graph)){
                    return true;
                }
                else if (recStack[i]){
                    return true;
                }
            }
        }
        recStack[v]= false;
        return false;
    }
    public static boolean isCycle(ArrayList<Integer>  graph,int n){
        return false;
    }
    public static void dfs(int v,int[] graph, boolean [] visited){
        visited[v]= true;
        for(var x : graph){
            if(!visited[x]){
                dfs(x,graph,visited);
            }
        }
    }
}