Envío 6268

Código

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Scanner;

public class Main {

    private static HashMap<Integer, ArrayList<Integer>> directedRelations = new HashMap<>();
    private static HashMap<Integer, Boolean> unprocessedNodes = new HashMap<>();
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int m = scanner.nextInt();

        for(int i=0; i<m; i++){
            int from = scanner.nextInt();
            int to = scanner.nextInt();
            
            unprocessedNodes.put(from, true);
            if(!unprocessedNodes.containsKey(to)){
                unprocessedNodes.put(to, true);
            }

            if(directedRelations.containsKey(from)){
                directedRelations.get(from).add(to);
            } else {
                ArrayList<Integer> arrayList = new ArrayList<Integer>();
                arrayList.add(to);
                directedRelations.put(from,arrayList);
            }
        }

        while (!unprocessedNodes.isEmpty()){
            int node = (int) unprocessedNodes.keySet().toArray()[0];
            if(findCycle(node, new HashMap<Integer, Boolean>())){
                System.out.println("Yes");
                break;
            }
        }

        if(unprocessedNodes.isEmpty()){
            System.out.println("No");
        }
    }

    /**
     * True if find cycle, false otherwise
     * @param node
     * @param recursionNode
     * @return
     */
    private static boolean findCycle (int node, HashMap<Integer, Boolean> recursionNode){
        if(directedRelations.containsKey(node)) {
            if(!recursionNode.containsKey(node)) {
                recursionNode.put(node, true);
            } else {
                return true;
            }

            if(!unprocessedNodes.containsKey(node)){
                return false;
            }

            for (int relation : directedRelations.get(node)) {
                if (findCycle(relation, recursionNode)){
                    return true;
                }
            }


            recursionNode.remove(node);
        }

        if(unprocessedNodes.containsKey(node)){
            unprocessedNodes.remove(node);
        }
        return false;
    }
}